as both game developer and player, i think people tend to forget that posting about a doujin or indie game you've played and enjoyed is actually one of the best things you can do to make that developer happy.
even if it's as simple as "wow, this game is kinda good".
even if i don't write a long ass review, i always make sure to comment at least something on the itch page or talk about it on social media.
this works for games in a different language. i've had many fun encounters with japanese developers reading my english language thoughts.
you don't have to write long reviews like i do. i don't even do that most of the time. i just paste screenshots, make sure my tweet is searchable, and go "wow, this is kinda great".
creators egosearch and want to see their works be played. it's validating. i seriously recommend it.
i absolutely save every little nice thing i see people write about my games... that kind of thing is such a lovely reminder to me when it's a rainy day and making games suddenly feels impenetrable