You absolutely should feel free to criticize a game regardless of whether or not you pay for it. It does not need to be constructive either. If a game is, in your opinion, bad, then by all means say so.
Some of you all need to stop trying to protect developers from players. Any feedback should be welcome, regardless of how harsh or well written it is. The dev gets to decide what they consider valid and what they ignore.
Patreon has warped viewpoints on games like this so badly. Donating to a dev does not make you a customer, and does not make your opinion more valid. You also do not need to rationalize your donations.
Sorry, rant over. I just hate this idea that opinions should be filtered based on how much or if you donate. I think Lina can cope with someone not liking her game, no need to gatekeep.