The worst part is the default font, Computer Modern, which is absolutely deplorable. I'm not a big fan of the general style of "modern" fonts (a name coined at the end of the 19th centry when they still were actually modern). But, worse than that, Computer Modern is horrifically slim and spindly. I've read repeated rumours over the years that it was deliberately this way because the printers of the time used ink that would run a bit so the font was like that to compensate, but I don't know if it's true.

That's not such a big deal since you can obviously change the font. For a long time there were lots of text fonts but very few math fonts, and those math fonts that did exist would either have some symbols from Computer Modern or wouldn't have a suitably similar text font. But now there are a fair number of choices. Personally I like mathpazo (with Palatino for text) but I've found people used to Computer Modern can find this a bit much of a radical departure. (Edit: I've found a more conservative choice is Times for text and Utopia (MathDesign) for math.)

TeX does have a few small typesetting niggles. For example, if you set f(x)g(y) with normal small brackets around the x but large brackets around the y (because it's really a displayed fraction) then you'll find g is miles away from its argument but right next to f's argument. (I'll avoid opening the can of worms about what the root cause is here, but it's very clearly wrong in this case.) This is actually not that big a deal either - there are lots of problems like this but they're all fairly minor and small in number compared to the huge number of things typeset correctly. The only problem comes when people refuse to correct things because they assume that if TeX typesets it that way then that must be correct by definition.

I can't stand the fonts, don't like how it applies space, etc.

TeX is like a programmable pocket calculator from the 1970s, way ahead of it's time but today it's something that conspires with Word, Google Docs, and other dull tools to suck out the oxygen for sharp tools.