The ones that leap out of water to get you on world 3 were already quite stressful.
That fish didn't terrify me near as much as the angry sun though. Back then I often did "almost complete" runs where I'd just kept a lakitu cloud to skip the sun level from world 8.
Look, I was born in the 80s, I played Morrowind about the time it was released (closer to GOTY edition, but whatever), but even I have to kinda agree with your niece at this point.
Though its gameplay and world-building certainly aged better than Oblivion's.