I have a question

You have more than one single question I see.
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First question:
⇒ 'They nerf anti tunnel perks and suddenly Survivors can get off the hook for free if they Killer spends to much time around the hook? '

You say something here but how many times you have used the 'Anti Face-Camp' mechanic to 'get off the hook for free' ?
Honestly, in SoloQ the only time that I could used it, we have all the rest of the team around the PyramidHead's hook as the killer stays a little bit away enough to really avoid to increase fastly the AFC progression bar. Nobody on my team notices this yet.
So my bar has reached the 2nd stage before the 'free unhook' as you said. Then PH staying around, has naturally used his M2 to down me again so quickly (5sec or less ?).
I think this AFC is worst it.
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2nd. question:
⇒ 'They ######### out the Skull Merchant + Knight on top of their lousy map design and suddenly Killer's are not allowed to kick gens after a certain amount?'

After 8 taps if I recall the patchnote correctly.
Well, about the SM & the Hairy Knight, I think this change is only to encourage them to take more chases.
But it is still easy for them to keep a trigen, to use their power to defend him and as soon as they have downed someone around, they pick him up & hook on the hook near their trigen & still can slug any survivor around bc the hook is already used. This to secure a kill or 'defend' their gen.
So they can save their tap on gen and probably they can make 2k or more in this way.
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3rd.question:
⇒ 'Killers try to combat gen speeds and the meta gets nerfed because of…. reasons? I honestly dont understand these nerfs towards anti tunnel and anti gen perks in general.'

Chases take too long for killers & they probably don't have time to do enough to be rewarded enough at the end. So a meta gen build is required.
And you don't understand these 'nerfs towards anti tunnel & anti tunnel gen perks in general' either you aren't tunnelled each game or you don't use this bugged nerfed DS for 4 sec, or this Off The Record/Borrowed Time that it can easily counter by a free hit directly after the unhook.
Add to that, you still have many survs that they absolutely want to proc their DS during the match. So they aggro & be openly provocative to the killer to use it…
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I think to respond to your questions, BVHR resplies to the players community in this way.

i still don't understand why knight was ever bunched up as 3 gen killer. he is chase killer that rely on summoning to zone survivors. He just isn't particularly fast at downing survivors despite being a killer geared towards chase. He doesn't get rewarded for landing guards on top of the survivor. All the survivors can outrun his guards, so he only ever gets effective when survivors are in the corner and are unable to run away from both him and the guard itself in the pincer. There are pathing and strategies to delay the pincer. Delay it enough while doing gens and he falls flat as a killer.

I don't think more slowdown perks being invented cause perks to get nerfed. Hex:ruin was first slowdown perk to ever be released and it was meta since the very start. Pop goes weasel went into meta as soon as they made it an effective perk. The other slowdown perks introduced alternative options for the killer to select. they keep getting selected because most of BVHR's other killer perks are drastically under-tuned compare to game-delay perks. The other reason why they keep getting selected is that the killer's base game-delay for being successful at the chase is atrociously bad. BVHR still has made little to no attempts to improve the killer's game-delay presence for being effective at playing the killer. as a result, the killer player are forced to use perks to do create game-delay presence. High pick rate leads to high effectiveness rate which leads to nerf's. Just a big giant snowball effect.

Three words:

Nowhere to hide

This perk was the last piece to solidify the cobruption meta that inevitably led to the 3 gen meta as well.

You also have to consider that knight is a zoning killer and the guards can only patrol a limited area. So in addition to the perk, this was one of the killers who excelled at holding down a relatively small area indefinitely (i.e. 3 genning). This wasn't a typical hag or trapper trap you could avoid or disarm, it's a decent area of effect that patrols the area and, at worst, notifies the killer where you are. At best, it takes a health state while the killer patrols the other gen.

So knight was part of the meta problem, and basically a lot of killers had that neuron activation moment that holding games hostage was easier than chase, right at the same time.

Did you stop reading after the first sentence?

Knights power is also most about zoning a decent sized area, which was a big reason people started 3 genning as well.

Having a power that specializes in information or just outright denial / free hits for holding a 3 gen is a pretty big deal, especially since the 3 gen meta was widely hated and took far too long to address.

Just because SM ultimately did this better, doesn't mean that knight wasn't also really good at it to begin with. That's not something that doctor, Nemesis, or onryo have.