I love using it and despite being crap at design, I’ve managed to put some stuff together that I think is not half bad. (And I remain mighty impressed with their business plan, too!)
Their opposition to abstracted utility classes means that anything you want to do has incredibly long, unreadable classes. Its quite a bit of work to abstract away the bits that you want.
https://daisyui.com is my absolute sweet spot for abstraction. Its a bit limited, especially compared to TwUI and flowbite but its developer experience is a joy.
And to say that design "just doesn't matter" while you're in fundraising mode, i think is also incorrect. You don't need perfect design, but it has to look pretty decent. It's in people's nature to be turned off by ugly/obsolete looking web pages.
this ^^ was you, right? pardon me if I don't hold your opinion in high regard
But, at the end of day, the best option will be the one you're most comfortable with.
Anecdotally, I've sometimes seen better quality websites for a lot of the little "polish" things like accessibility (which isn't really "polish", is it?) from the laziest "just use Bootstrap" developers than from the most hardworking Tailwind developer+designer combos.
If you're not a designer, it takes a non-trivial amount of time to add the utility classes you need to get something that looks passable. Quite simply, it gives you too much control over something that just doesn't matter for an MVP.
There are great component libraries out there (I'm a fan of Chakra) that give you sane defaults so that you can get something off the ground, while not focusing on something that doesn't matter at the MVP stage.
Maybe Tailwind + Radix makes more sense after you raise funding...?