I want to preface this by saying I don't mean what I'm about to say in a bad way, but long story short, if the author wants to pack the game full of foot fetish content (or any other fetish) than they are allowed to do so, it's their game. Saying they shouldn't put something in or make it avoidable because you or other may not like it is a selfish mindset. If you don't like that sort of content then don't play the game, don't try and influence the author to change their vision.
First of all, I agree completely. In the end it is the author who has to decide and they should decide by what works best for the story they have in mind, even if that means losing Patreons. Because not only is it better for them when writing and having fun themselves, it is also better for the players/VN readers. Everything an author does just to please "the crowd" will probably come out stale. Including a fetish they don't like themself will mean they probably don't know what it is about this fetish and just mean "the technical definitions are met" but without any feeling or coherency. It'd be akin to inserting a sex scene into a novel which didn't need it "And then he went over her and inserted his penis into her vagina. Both moved back and forward, until they moaned and came". Technically a sex scene, eroticism <1%.
Also, some fetishes and the story go hand in hand, and both excluding or including them will just feel wonky and off. Assume you'd put in the tried and tested "landlady and flatmates" to avoid incest, not to please Patreon, but to please non incest fans. It'd be ridiculous from the beginning, only that those you wanted to please will obviously know that they're still mother and sister despite the labels and not like the game. I think it is most prevalent on these forums with NTR, where both the pro and contra crowds will ask for games to be changed despite it going against the whole spirit of the game.
However, having said that, I'd like to also add that "optional" may be a way out if you're going for many fetishes while getting as many fans as possible - be it for commercial reasons or just because you like to make people happy. The longer the tag list gets, the more likely it becomes that while attracting some new fans you're losing more for which this fetish is either unbearable or the straw that breaks the methaphorical camel's back of things you have to "skip" to get to what you like. This is probably different for different tags in how easy it will be. Taking oral and anal out to go for straight vanilla is probably pretty easy most of the time without ruining the story (albeit a bad example, since they're rarely requested to be removed) while fetishes like furry tend to be the core of the story they're in and rarely able to be taken out.
But if you see the opportunity to fulfil a fetish without it being essential, and then make it optional (by which I mean "obvious to avoid or get" - games where deciding on whether you want white wine or red wine on day 2 will open or close BDSM on day 12 can go eff themselves), that can be a good crowd pleaser IMO. Of course in the end I need to come back what you correctly stated: it needs to be up to the dev and what they want and how they judge the story with or without the stuff in question.
(Edit: spelling)
