How many hearts and stamina did you have for your first dungeon?
Rito one is the easiest, I did it immediately with 4 hearts and no stamina upgrades. In order of easiest to hardest:
Rito (Had the best boss fight)
Zora
Zonai (Accessible whenever but the quest lead up requires previous dungeons to be finished, also health gated requiring 11 hearts)
Hyrule Castle (No puzzles, just enemy gauntlet, and the layout is actually simplified due to collapsed hallways and such, progress gated until after 4 regional dungeons)
Goron (Not really hard, the layout is just really annoying to navigate)
Gerudo (Most like a real dungeon, but still really lacking)
I still did them with no upgrades beyond the health containers from previous dungeons. I think the bosses are much easier than the blight ganons despite actually being unique now, the gerudo having the hardest, but that was only difficult because the framerate was in the low 20s the entire fight.
The Rito and Zora ones are the most divine beast styled in terms of layout and gameplay. It's really weird because they really stand out as far below the others thematically and challenge wise, its like they made them first and then later decided to lean more towards traditional dungeon but didn't bother to go back and update them.
If you are wondering what order I did:
Rito
Zora
Gerudo
Goron
Hyrule Castle
Zonai