Perhaps you have not had the pleasure of discussing stealth with anyone of the “if it doesn’t work 100% of the time then it’s completely worthless” mindset…
I'm not saying it doesn't work, the problem is that most sleeper volumes are ambushes in t3+ pois, and most of the time the zombies are always hidden behind blocks so your not able to use your stealth to snipe from the doorway like you should be able to. Like if I could open the door and snipe them i'd not complain. But the fact they are almost always hidden behind a block kinda well.. blocks that, thats not even saying if just opening the door doesn't trigger the entire pack of zombies in that room as it often tends to do, no matter how high your stealth perks are. Some ambushes are expected like loot room ones, I got no problem with those as they make sense, but every other random room in some random house being a ambush? no just no. Stealth does work somewhat, but the devs seem to activly try to do as much as they can to ruin it for stealth build players. The fact almost every sleeper in a poi is hidden behind a block is pretty big proof of this, as is most sleeper volumes in t3+ (sometimes even t2), immedatly knowing where you are and waking up second the door opens or you walk 1 step into the room. I'd be ok with it if they would "wake up" but then go into wander mode, as in they don't KNOW your there yet, they just wandering around like a outdoor zombie that hasn't noticed you yet, still can get sneak attack bonuses on them as long as they don't see/hear you.
TFP has been steadily taking away choice from the player, and stealth playstyles is the most recent victim of this. Last big victim was underground bases basically not being a thing anymore since zombies can magically dig now. Things where the devs have activly done stuff to try to curb certain playstyles. Like I said with sleepers behind blocks always, and such.
I mean, stealth playstyle is already pretty slow in terms of clear speed, as crouching all the time slows everything down. You could go in guns blazing or whacking with a club and get it done faster than doing it with stealth. So I never seen the need for the extra BS to prevent the playstyles.
Also for the A16 "issue" ask pretty much anyone who played it, they will say the skill system is far better than what we have now pretty much. As it has much less gating than the curret stat system does. It did need some tweaks though, like craft quality swapped from the action skill, to the related perk, Like miner 69'er for tools. That was literally ALL that needed to be done to fix the a16 skill system, and instead they redid the entire system and made it far worse than it was. Thankfully there are mods, most of the good mods pretty much always have some sort of action skill system as its what the players want. Why won't tfp give us what we want? No one wanted this stat locked system we have now, at least not in the current form it is. If it was done differently it'd prob be ok, Maybe 3 Categories, one for combat, 1 for defense, and 1 for crafting. The fact that each weap type set is under a diff stat personally annoys the hell out of me and many others. Maybe make a attribute point system? where instead of using perk points you get a new point on level up that is only for attributes along with the usual perk point you'd get? This would kinda fix the issue somewhat as well, and shouldn't be hard to implement either.
Many players are fine with a17-20 because they never played a16.4, so they don't know what they are missing skill system wise. They see what we have now and assume thats how it always was, as most games in Early access don't redo the entire skill system every new version or 2 like 7dtd has been doing for a long time. I started in A9/10 or when it was released on steam. Pretty sure was a9-10 ish.
I am just glad mods are a thing, as they bring back the games glory days, I find vanilla horribly boring and barely play it other than a game or 2 per alpha to mess with the newest stuff and then wonder how the mods I play are going to put this in, or if they don't just trash the whole system (Most mods throw the whole vanilla stat system in the trash can and do their own far better thing), before I just play something else and wait for the mods I play to be updated for the new alpha which is where I then spend most of my time. Vanilla honestly needs a tier above steel for materials (Tungsten? maybe Titanium?), and some zombies above radiated as i've said before, like even if its a "after game goes gold" thing would be fine for now. So at least we KNOW it's coming.
I wonder though, do the devs ever play some of the bigger mods like Undead Legacy, Darkness Falls, and Apocalypse Now? Some of the ideas and stuff they put in is amazing and would be great for vanilla. Highly suggest they play some of them to get some idea's, as they desperately seem to need some to get the game out of the stagnating rut its been in for years.
This is just my opinion as a player who's been around for a very long time.