Why are so many people suddenly thinking that this is a problem?
I dont see problem with that, granted I have (probably) been playing this game far longer then you but it never was a real problem for me. If I got ambushed/ walked up on by the AI it was usually my fault for not paying attention to the game. What is wrong with that? After all, the game is supposed to be more demanding then your usual CoD or Battlefield. I mean, it is fairly obvious that the Game is very Escape from Tarkov and Stalker inspired and those games can be Hell if you do not pay attention.
I think this game would be better if it was more CQB focused. As it stands now, you might as well just actually play Arma, Tarkov, or any Battle Royale. There are PLENTY outdoor "real-life sim" shooters out there. I personally like the enemy AI but I don't like how far they can both hear and see you from, but that's also passable. My main issue is with their movements. You have to play like if you were playing Ready or Not or Arma, but they fight like if they were playing COD or CSGO, it's ridiculous.
You tone that down, make the game more CQB (indoor) focused, remove the stuns, remove the gacha (or make it only for cosmetics), and you got yourself a good shooter that as a bonus, has H scenes.
If you are going to play a game that feels like a worse BR, is played like one, then why don't you just play a BR?
As somebody else mentioned, the scenes aren't that unique either, so why would anyone buy this game instead of something else?
Yes, I know that this game isn't finished, and I see that you don't like the recent reviews this game has gotten, but you gotta understand, they are there so that the dev hopefully reads them and does SOMETHING about it. I played this game about ~1-2 years ago, where all the enemies were tentacles and zombies with a bleed system. The game then was boring as fuck, and while some things have changed, the game is still boring as hell. As somebody else mentioned, if I had bought this on steam, I too would have refunded it. In my opinion, the focus of this game should be: Game first, Eroge second. Focus on making the gameplay enjoyable and THEN focus on the H-content. If you are unable or unwilling to tone down your AI, then try making it CQB and transition to something open in the later missions (sort of like how the Metro series do it).
It ultimately IS the dev's choice to choose whether to listen to the feedback or not. That being said, if you have integrity and are thinking of making a quality product, then you'd at least listen and answer the player's concern. You are NOT making a game for yourself, you are a making it for as many people out there to enjoy. As mentioned earlier, this is NOT fun nor enjoyable.
I also don't understand why you would change engine half-way through, what's the point? If anything, you do it after your game is finished as a free-patch update (remaster) and leave the legacy (original) version available for anyone that can't handle the new engine.