Some areas will trigger zombies no matter what. I don't know why this exists in a game that supposedly lets you choose how to approach challenges, but then again TFP have a habit of implementing conflicting mechanics.
Silliness of the trigger mechanic aside, I think you can still use stealth in such situations by moving away from where you triggered the zombies and crouching out of sight to reacquire stealth.
Its more they are trying to force you to play in a certain way in a sandbox game which is a pretty stupid idea imo.
I mean people liked to make underground bases, not everyone cares for horde night, Nope can't have that. I built underground because everytime I try to build a base the SI system @%$*#!s me, and I end up putting 1 block to many and it collapses my entire damn base, if it was JUST the most recent block that dropped it'd be fine, but nope, has to take entire row, which then cascades and can take out the entire base other than the side walls.
Some people would swim on top of lakes to avoid the horde/for saftey at night... Nope not allowed to have that either, as zombies can swim now, and even more stupid THEY SWIM FASTER THAN THE PLAYER CAN what the @%$*#!?.
Some people like to build nice bases, Nope can't have that either now because the zombies know the best way to bring it down, so your forced to build a base that cheeses the AI if you don't want your base to get totaled. I haven't built a base in a while due to the SI system and the fact I can't make my underground home anymore. I usually fortify certain poi's.
Some people like stealth, but we can't have THAT either, what with the garbage/glass piles in front of the door and behind doors in the intended path in the silly dungeon style poi's, yes we can destroy them, but it'd be better if they had 1 block HP so ANYthing can destroy them in 1 hit, instead of having higher hp. Then you have zombies that are positioned in ways to screw stealth players, in closets, or on the otherside of a obsticle so your forced to get closer to hit them. THEN we have the sleeper volumes that just wake up the second you walk in the room no matter how good your stealth is.
Stealth would be better if it was like fo4/76. There is 3 states: Hidden, Caution and Danger. In Hidden your completly hidden nothing has detected you, you get sneak attack bonuses. In caution status something has noticed your presence but they are not sure where you are so they are looking, In this state you can still get sneak attacks. Then Danger state, this is when the enemy has found you and "locked on" no sneak attack bonus. Its silly that when you wake up a zombie in anyway, even if it has no idea where you actually are that you lose sneak attack bonus entirely. It should only be lost if they actually seen you and are chasing you. This would fix stealth being broken, as you could say, throw a rock, or fire an arrow near a zombie to wake up, then when it comes out of cover, BOOM headshot for sneak attack bonus damage as it doesn't know where you are. The main reason people use stealth is for the sneak attack bonus, as the zombies are way to sensitive to sounds anyway, your not going to be sneaking by much of anything, nor would you want to, that zombie is exp, and a threat, but the fact if a zombie gets woken up in anyway you immedatly lose sneak attack bonus damage is the main problem with the current system.
The dungeon style poi's: These need to be removed if your going to insist on this garbage linear loot stuff you spewed out in a19. Nothings worse than clearing a t3 poi out only to find a chest full of nothing but stone weapons, or opening a safe to find the same. The dungeion style poi's were great in a18 with its randomized loot, it was ALWAYS worth to loot everything at any GS, in A19, I skip many loot containers as its just not worth opening them at all due to knowing exactly what i'll get out of it, its a dumb way to play a game like this, and again its something the devs seem to wanna force on us. Put loot back how it was in a18, add the new items then for frigs sake leave it the hell alone as it was not broken in a18, the loot in a19 is the broken one, as it has sucked out almost all the fun of looting in the game.
I'd also like to see more stuff added to the game options, like the ability to turn on/off digging zombies, or set it so only animals can dig, and turn on/off swimming zombies, those sort of options so we can play the game how WE like to. Just because the game has mods is no excuse to be lazy and not include the option as a default setting. Look at Ark survival evoled, there are so many sliders you can use to customize your game, we need something like that in 7dtd.
Every other Alpha since I first got the game in a9 or 10, i'd usually be playing experimental for 8+ hours a day for weeks, in A19? i've prob played less than 30 hours total since experimental as the game has just been ruined by the loot change, its taken all the fun I had out of the game for me and apparently for many others as most people on here seem to HATE the new loot system. Lets be honest with the lack of content the game has, fun looting was really all it had going for it currently, and that was taken away in a19.
TL

R Devs, please stop trying to control/force us to play in a certain way in 7 days to die, its supposed to be a sandbox style game, but its quickly turning away from that due to all the restrictions that keep being put in.
These are two of my biggest complaints about the game; fixing this and adding option sliders would correct almost everything the game is lacking in.
You forgot fixing the loot back to a18, as the currently system in a19 is complete garbage and ruins the game pretty much.