Yes, there are elements patrons shouldn't touch. Be it core game design, the main story, characters personalities, etc. Letting people change the game's overall direction is definitely a bad idea. These things should be planned long in advance.
This, however, is something I dislike. A dev should have a clear plan when to release every part of the game. I don't like updates focused on a single girl, for example. That is a sure way to get me off patronage, if it depends on a vote. Yes, the developer will eventually make all of them, but if I happen to like only one that also is not very popular? I can end up looking at two or more updates with nothing of interest to me.
One of the many things I like about Notty is that the order of release is entirely up to her to fit the chapter framework and the story in the best possible way. Every route gets something in every update. It's for everyone, not just those who won the poll.
There are some devs who don't plan enough and do what you suggest, but inherently letting patrons decide specific content doesn't necessarily mean lack of planning. It can be actually be the opposite. The dev may have plans or ideas for more content than what can be fit in, so he lets patrons decide, while he is happy to do any of the options. A win-win.
I do plan to have large participation of patrons on certain important elements. All the options that I will offer, however, will be prepared. None of it should look like "I don't know what to do, choose something from me" I imagine I will have a ton of stuff written that will never see the light of day, but part of the fun for me is not knowing exactly everything that will be in the game. It's a bit of a team effort. I have complete creative control, but patrons can narrow the focus down to some extent.
Notty, by the way, also does content polls for high tiers from time to time. It's more of a side stuff where she has multiple ideas (lately the Scarlet Pirate for example), so she lets patrons choose one of them, but the principle is there. Patrons participate in the development. Surely you wouldn't say there is lack of planning here, would you?