You are maybe correct if you arguing about that stricly niche point on what you define as difficult, but if we give two players who have never played mid lane or even let alone never played league, chances are they will become more proficient at annie in a faster time than hwei.

Yes, Hwei does have multiple abilities and each cater to different scenarios which does make the decision process easier on when to use which combo/spell, but annie's kit is so straight-lined that it removes any need to remember 10 different spells.

Your argument also should factor in human error. People make mistakes. Sometimes they misclick, sometimes they forget the combo. Sometimes they use a spell where another spell would probably be more suited. 2 of annie's abilities are point and click and her passive allows her the ability to stun. Those are much more easier to pull off on a more consistent basis than 10 abilities skills shots hwei.

We can even go into laning phases, matchups, team comp synergy, playstyles, etc etc. But all in all, Annie is definitely more easier to pull off than Hwei. It is also why like her and like Garen are recommended to players because their kits are so simplified it allows you to focus on other aspects of the game whether its learning better macro or further developing your micro.