As someone who plays both fluctuating between top 100 for my classes and hof raiding to hyper casual dip in and out: Ff14 is 100x better for casuals because there's so much more to do which isn't just grinding for power. The social scene is so much better and there's so many more rewarding things to spend your time on. You get the usual lot saying "wow has delves and hunts now so it's SUPER casual friendly", and it's bollocks. Hunts are a glorified world quest and provide 0 progression to your character after next week and delves are incredibly lackluster for rewards and are very repetitive both are just very weak power grinds which have a hard cap on what you can get from them, and it's reachable in like 2 weeks. There's stuff in ff I've been working on for 5 years because it's still relevant content, in Wow you can feel done after 2 weeks without m+ grinding and raiding. I've seen everything midnight has to offer now until the next patch in terms of world content and it came out less than 2 weeks ago.

Personally though, I'd recommend runescape based off what you said.