So I'd get notified of game releases in a certain tag/category? Does something like this exist and if not, could it be done? Thanks!
That feature doesn't exist, but a "workaround" to it is that there are people on Itch who keep neatly-organised collections for... well, everything. And if you follow someone you'll be notified when they add projects to their collections.
If you find a good collection curator it's about as nice, if not better, than following a tag.