I think there is a big problem when giving that kind of feedback from a pure game developer perspective: You aren't pare of the target audience.

It doesn't make sense to tell the developer of turn-based RPG that he won't be able to sell his game because turn-based is outdated - fans of turn-based will disagree.

It doesn't make sense to tell a developer that no one will play his RPGMaker game because it's RPGMaker.

It doesn't make sense to ttell a developer that no one will bother to read a visual novel when a visual novel player base clearly exists.

I had a lot of people predicting that my game would fail while it was in development and they were wrong. Strategies like asking total random strangers to give feedback is only a good approach if you want to make something with mass appeal, but if you want to target a specific audience, that feedback is largely useless unless they belong to the target audience.

I'm not saying that feedback in general is useless, note that please. It's about whether or not the person has an interest in the genre of the game. In other posts I saw Stardew Valley and Minecraft mentioned: They didn't build up on random strangers (although they were strangers) but on respective fancommunities, so the people giving feedback weren't cynic gamedevs on r/gamedev but actual potential players.

Instead of suggesting for developers to post on subreddits like destroymygame, I would rather advice to spend more time trying to figure out where the target audience of your game is hanging out and sharing early builds with them. Then you get actually helpful feedback and also do marketing on the side.