Silverhand

The Mario & Luigi games are similarly approachable and good RPGs, Superstar Saga (the first one) especially. They are handheld games so maybe a bit more difficult to play together with someone, though you could emulate them very easily to play on a more suitable device.

Sea of Stars also might be worth a try. Takes a lot of inspiration from Paper Mario.

Your Only Move is Hustle is pretty much exactly what you described.

Enforces everyone to reset at the same time and not use gear and stuff from previous characters. Some people care about leaderboards and those usually reset at the same time. For other ARPGs with a trade economy that being reset is often the biggest draw, but that doesn’t apply to D3.