until it reaches a point where 80-90% curation percentage is needed if you want to get votes

I don't think that would happen, universally, but I also think there are cases where 80-90% curation makes perfect sense as a way to encourage risky voting on less-known or less-mainstream content.

Really excellent posts (high potential earnings) would get votes even with a low percentage. If you can vote on a post with 10% curation rewards but likely to reach $100 or a post with 100% curation that probably won't exceed $2, which do you choose?

I think we'd see different types of content and different authors offering different percentages, in a sort of curation-market way (more obscure content and authors would have to offer more, but at least they have the option to offer more and get noticed).

I do see some issues with UI but only pro curators and bots need pay attention to most of it anyway (like most of the low-level curation rules). Both can build their own tools or a market can develop for better tools than the baseline (steemit.com) platform (as is the case now for features like beneficiaries).