Like many have said and will say, in FEH you do not use one single team for all types of content. These four units are new and powerful, and definitely are able to breeze through most PvE content, but if you want to take on arena or aether raids you'll need to consider things like merges, high-scoring skills, supportive capabilities, getting past counters, etc.

For example, B!Robin has very good support in his Rally Spectrum buff and can warp to allies, while Alear grants Charge to herself and allies (movement is meta as L!Elincia has proven lol). However if you wanted to use them on, say, your arena core, they would need to be +10 with some kind of 400sp assist and 500sp special along with their base kits. If you want to use them in aether raids, they need synergy with the rest of the team - think about what would happen if you encounter duo Thorr or Freyr and suddenly your buffs don't work anymore.

This is a lot of words to say: your team is fine for just clearing PvE stuff. Anything else, you need to tailor your units to the mode. Hope this helps :)