"As of January 2022, the platform had approximately 40 million monthly active users."[0]
In 2022 they had $30M expenses, so the cost is somewhat under $1/user/year.
They said the minimum donation is there to reduce the viability of scammers using it to check if a stolen credit card number is valid.
I played and enjoyed Chants of Sennaar and Jusant in the last few months. A recent standout game for me was Tunic. Check it out, it might suit you well as much as it did me. It has fighting but if you want you can enable easier combat or even "no fail mode" (invulnerability) from the menu. The game has a ton of hidden secrets and puzzles while being pretty and friendly to look at like the other two games. It is a great experience with or without the combat parts.