Overwatch is very pretty (both games are in my opinion), however it is so busy. There are no visual cues in the design - characters and scenery share the same palette, important elements (like payloads, turrets, etc) don't stand out. No way of knowing where the important flow points are other than to play the game a lot (no indication of where the playload will go). Having had such a great example in TF2 that did all this so well it was just sad trying to get to grips with Overwatch.
League of Legends on the other hand had an amazing visual update a year or two ago and they explicitly addressed all these kind of issues. Making sure the map doesn't distract from the important in game information.
Both games have a lot of characters and a lot of knowledge burden for the players, so anything they can pull off the player makes a big difference when first starting.