It’s your island. Only you can decide what villagers you want, but the fact that you created this thread shows you’re not certain about him. Let him go and see if there are better options.
Well it's up to you, I don't want to tell people to make decisions they will regret
If you have attachment to him I personally would keep him regardless if he matches your theme or not if he is special to you
but if you only value him for your theme and he matches okay but you don't have an attachment to him I might consider letting him go if your looking for a change and you might find a villager you like more that you have more attachment to/matches your theme better
whatever you end up doing with Julian it's your decision
I voted boot him , but for me its more of get to know other villagers and aesthetics and although dialogs could be better they do sometimes say something here and there about their likings and paths etc, so for me once i get their photo im very happy to let them move on when they feel ready. Plus with the DLC we can change exterior and interior to match your aesthetics