Good recommends, added them all.
best part is all of them have (or had during the festival) a demo where you could give it a try. some devs disable the demo afterwards or it bugs out if you start it from it's folder because it needs steam in some way (like grime because it wants to trigger achievements), but that shouldn't matter for release or while the demo is officially available. devs are also active during that week if you wanna
call them names provide feedback, have suggestions or whatever.
some games I didn't mention because they're older or don't have a release date yet: tandem: a tale of shadows (looks like a ps2 game but GRAFIX!! aren't that important for a puzzle game imo and it's a rare 3d instead of pixelshit), little witch in the woods (personally waiting for that one). glimmer in mirror (nothing special in the demo so far, but gorgeous as fuck), beacon pines (another one I'm waiting for, adventure game with interesting "what if" timeline mechanic), undying (more casual isometric this war of mine); lost words: beyond the page stuck with me for some reason even if it felt slightly pretentiously "artsy" at times, prolly gonna pick that up during a sale. a space for the unbound (another adventure, from indonesia I think) had the same effect, but that one's not out yet.
there were loads more plus the ones I forgot to wishlist or bookmark (and I don't want to spam/shill too many). there are some by others over
here.
I'm really looking for RTS, like Iron Harvest and Zero K. Doorkickers 2 and AoE 4 might scratch that itch.
mostly stuck with metroidvanias and other stuff I could play comfy on the couch via pad with the odd turn based rpg/management sim thrown in, so didn't really check out strategy (there were way too many frigging games for a single week).
however, valve was smart enough to leave the page up, you can still check it out here:
https://store.steampowered.com/sale/nextfest_june2021 (that's only the highlights, there's more when you scroll down and filter the tags).
next one is up for october, more hyped for that than e3 and gamescom combined.