I'd guess that the current producers/showrunners/decision-makers found them not alien enough, so their added physical trade-marks from 1987 (they had nearly no distinguishing marks in 1966) got further boosted. Bigger heads, more ridges, sharper teeth and fingernails. To misquote the 6-million-dollar-man: Gentlemen, we can rebuild them. We have the technology and the budget. (I'll refrain from using the rest of the quote)
As for "this spore drive is hella stupid and the giant tardigrade is dumb" ... isn't trying out new whacky things a trademark of Star Trek? Technology and what it can do is, if you go solely by the tv-shows, rather flexible and new things and new ways how to use old things constantly gets seemingly invented only for that one episodes sake. Far too often for my taste did the old shows stumble into the 'Reed Richards is Useless' trope because rarely was there a large overlaying story-arc and therefore the necessity for lasting changes.
DS9, VOY and now DIS profit from not adhering to the old monster/problem-of-the-week writingstyle. Hell, in TOS and TNGs earlier season it hardly matters in which order you watch the episodes, recurring characters and/or lasting consequences were few and far between.