Either buff familiar/summons or remove them. This is a flat issue with summoning and familiar in general. It either needs to scale with the player or not be there. Because it becomes a waste rapidly.
Knowledge base: When a wizard attacks an enemy, they should be rolling to see if they know what damage times will affect it or not. Example; Imps in the beginning if you took firebolt they are taking half damage but there is no indication as the players knowledge grows in game, there should be markers for indication.
With spell casting, since you already use terrain and surface effects. Really should look at the players companion from the first expansion in D&D because it allows control mages beyond enchantment. Which should also be a thing. The big attraction of wizards and warlocks is the ability to play a control mage. Otherwise just user sorcerer since they actually do damage effects pretty much exclusively.
Add in ways to obtain proficiencies especially for weapons and armors. Its an alternate rule found in the Dungeon Masters manual but a very good one. The big draw of making a player character is to feel above the standard templates, it will help with the role playing aspects. The first two games, allowed this with party composition, dialogue choices and class choices which could generate that effect a lot.
Auto pass checks; I have seen where you need a 1 or higher to pass. Just add in an option to automatically succeed. Because the dice roll effect literally becomes a loading screen. And yeah that will get old fast.
On the whole its solid for early access and fun. But there is some need for improvement.
All of what you wrote was really well put, however i specifically really resonate with these. Specifically, i think there are certain alternate rulings that could specifically benefit the video game format and like you mentioned ways to obtain proficiency is one of them.