Changes you think were unnecessary?

Implementing MMR. The vast majority of the community does not like it and wishes we’d go back to the old rank system.

The rework for Built to Last. A perfectly fine, balanced, fun, and unique perk, turned into a generic locker perk. It may have been weaker, but it felt way better to use.
Old Built to Last was unique in the sense that it felt like a third add-on for your item at the cost of a perk slot. It worked passively rather than requiring you to do a second objective to activate it. The new one is just so forgettable.

It was really cool and well-designed when it launched. Felt like a portable battery pack for your item.

The worst part is that nobody asked for BtL to be reworked. People probably asked it to be buffed at best (though I think it was fine as it was).

All killer nerfs with the exception of maybe Nurse.

Legions Iri pin losing its global terrius.

MMR in theory works perfect for this game. But this version has just been terrible. Always sweaty as killer because gen speed (because they balance on rock bottom survivors), and always sweaty as survivor (because you're trying, the killer's trying, and your teammates are not). This is what you get when you balance off just kills and escapes, because you're looking purely at outcomes instead of what actually went down during the match. How many games have survivors thrown, giving the killer 2-3 free kills trying to save 1 guy, after owning him all match? How many matches has a survivor died for no reason, because their 3 teammates couldn't pull off an absolutely free endgame save, or because they couldn't get their Adrenaline/Hope to prock in time because that last gen that should've taken 1 minute to do took 3? So we need to start looking at other factors like gen speed, hooks, and SWF, make MMR strict again so that 100-hour players aren't constantly put with 3000 hour players, and only then will we be able to start having really good balance again like we had when MMR first dropped.

The old ranking system was terrible, and was basically random matchmaking. Don't you remember the years and years of having it, where nothing was being balanced properly because the devs had essentially no data to go off of? We'd have the same problems with it that we have now, twice over. "Oh, I didn't bring meta perks vs this decent team. Guess I lose." And "Aw man, I feel bad for bringing meta because these guys took 10 minutes to do 2 gens." We need some level of consistency in our matchmaking. The game will never be balanced otherwise. Put the players with game knowledge and experience in the highest MMR, the day-1/month-1 beginners in the lowest, and the up-and-coming learners somewhere in-between.

Them killing Mangled like that is basically sending a message that killers splitting pressure is a bad thing. For noobs, yeah, because with experienced players the strategy was never an issue as they could each hold their own when the killer came. So what's the alternative to splitting damage? Tunneling, which everyone is also against, and has been nerfed because of base BT and all manner of anti-tunnel perks. So killer has no good options right now.

I'm guessing the reason they nerfed Prove Thyself is because it was overkill with SWF and useless in solo. In solo for some reason, survivors are allergic to working on gens together while that perk is in play. SWF right now though can still use Prove Thyself because of the communication. If we look at it when compared to Deja Vu, the model gen speed perk in my eyes, it's a bit better.

I could write an essay.

1. MMR. Simple as that. Rank-based Matchmaking was fine with a meaningful Rank Reset (back in the day it was 10 Ranks or so, from Rank 1 to Rank 10 or 11). You had great games for the first three weeks after Rank Reset and only the last week was wonky. They first made the Rank Reset smaller, which meant that bad players were back in Red Ranks faster and then introduced MMR. And the way it is implemented is just dumb. It was clear that there is no way to do an accurate system, simply because there are too many factors. But basing it solely on Kills and Escapes is the worst. I can run the Killer around for 5 Gens and die to NOED and will be the worst player on our team. Or I can get 9 Hooks and a 1K and am worse than a Killer who camped their first Hook until death and got a second hook and Kill via NOED.
2. Addition of other versions for MacmIllan. The maps were perfect, the best Realm. And all the second variations suck for one reason or another.
3. Coldwind in Daylight. Maps were too bright anyway, I was joking years ago that it is not really "Dead by Daylight" with that brightness and then they introduced daytime maps. Coldwind really is the ugliest realm by far including the non-reworked Swamp.
4. Haddonfield-Rework. The map was not that bad before the latest Rework. Then they went to town on it and did everything at once. Now Haddonfield is probably the most killersided Map.
5. Nerfing already niche Perks - mainly things like Botany Knowledge, Calm Spirit and Pharmacy. Those Perks were totally fine before and they decided to "buff" them, but added a Nerf to all of them. I think the worst one is Pharmacy that it is only active when injured, meaning at the time you would actually need a Medkit there might be no chest anymore.
6. 1 or 2 of the three Nerfs to Adrenaline. IMO Adrenaline would have been fine with just removing the abiliy to wake up against Freddy. But adding that it does not work when being unhooked or the reduction of the Speedboost is just too much. If they really wanted one of those would have been fine, but not both. In the end, Adrenaline is a Perk which might not even activate and only activates onces in Endgame. It should be stronger.
7. Adding Voicelines to basically every character now. Some are just outright annoying (e.g. Alan Wake, who ist just screaming all the time). Would be better if they would actually have an option to mute those characters.
8. Giving Nurse a Mangled Add On after removing her synergy with Sloppy Butcher. I dont know who was the mind behind this, but giving her basically the Perk she just lost as an Add On was just a really weird move.

Oh man, the voicelines. I agree with most of these already (I thought the initial Haddonfield rework was pretty okay, it had bad elements for both sides but it was balanced compared to how it used to be and how it is now), and the Pharmacy nerf continues to blow my mind two years later, but you're so right and you should say it. The voicelines were awesome the first and second time they did it, because it was a novelty, and you were hearing all these iconic characters say iconic lines in a silent game. Now everyone is jabbering on and it just feels so cheesy and overwrought. I don't know why, but Vecna in particular makes me cringe. He'd be so much more imposing if he wasn't cliche villain hamming it up.

I think giving survivors any voicelines outside the lobby was a mistake, and the killers that do have lines should say them much less than they currently do (looking at you, Chucky.) The silence was a big part of the atmosphere of this game and the addition of all these cocky voicelines moves the feel more towards a typical choose-your-fighter game.