Not a GoT watcher, but man do they ever need to turn their lights on. So hard to see.I think we are fine with the Valar (in general) being taller than the Maiar (in general), and also with Morgoth taking on a 'giant' form for his 'tyrant of Angband' look (which he assumed at the Darkening of Valinor and keeps ever after).
I do know that giant humans tend to look ridiculous, but that's also possibly because of comedic associations, rather than it being impossible to make a scary (and not simply silly) 30 ft tall person (9.144 m). Does anyone recall any scenes on film with very large human-ish creatures that worked really well? By comedic, I mean the taller-than-buildings Stay-Puft marshmallow man in Ghostbusters and the 50 ft tall Calypso in Pirates of the Caribbean: At Worlds End. Clearly we don't want that! But just being big wouldn't make something automatically a joke. Game of Thrones had giants north of the Wall, and there were several fights with giants in that show.
I suppose the GoT giants are all different heights, but this particular one is about twice as tall as the humans, maybe a little taller. They don't come up to his hip. So, a 12'-15' foot giant looks something like this:
That's roughly the same scale as Last Alliance Sauron in Peter Jackson's films:
So, Season 8 Game of Thrones spoiler, but there is this fight scene between a much larger (very stupid) undead giant and a (very fearless) young girl. It's a bit one-sided, yes, but....
For reference, the two actors didn't interact with one another to shoot this scene. So, despite looking massive, the giant is played by a 7'1" actor named Ian Whyte, and the young girl is played by a 5' tall 15 year old actress named Bella Ramsay. The giant is likely meant to be...what...25-30 ft tall? I'm not quite sure.
I don't think I see the need for Morgoth to be that tall. He needs to be significantly taller than Fingolfin, clearly, but 15 ft (4.572 m) is already more than twice as tall. 24 ft (7.32 m) is 4 times as tall. So....30 ft...5x as tall is....really tall! The silmarils will look small in his crown if his head is that big. It's just...really big!