Quote Originally Posted by Amnestic View Post
Would it be all of a sudden if it required proficiency in arcana? If I was a high elf with the Firebolt cantrip? What about a third level wizard doing it? What about a fifth level cleric? Or an Eldritch Knight? If I'm a fifth level warlock and my buddy casts Fireball, can I make an arcana check to emulate it and cast it with a spell slot, even though it's not on my list?

I'm not necessarily aiming for an answer from you specifically, to be clear, but given the conversation I'm tossing it out there for others to ruminate and reflect on.
No to all. As Samurai mentioned, anyone* can jump, but channeling latent magical energy into a fireball is much rarer, therefore more than a skill check is needed. Arcana represents theoretical knowledge, but the Spellcasting feature or similar is needed to make that practical.

*anyone abled