Custom branding has worked out really well for some Fediverse servers. Poa.st is the only big one right now, but others have come and gone. It's just a matter of getting the word out and making onboarding is simple and easy.
I just made an account tonight and it was a nightmare. Clients overwriting each other's relays and follows, things not working that were just fine on my other keypair, etc. Things that have to be solved.
nostr:nprofile1qqs8nsk2uy2w529fs8n4tx60u7z553e4yx5dy2nxhw4elgjgawpqlaspz4mhxue69uhhyetvv9ujumt0wd68ytnsw43qzxthwden5te0wfjkccte9eeks6t5vehhycm99ehkuegprfmhxue69uhkummnw3ezucm0d9hxvatwv35hgtnrdaksarhv08 is already working on porting his brandable software to Nostr so you can easily run branded clients. Once that's done, you'll start to see more overlaps in the strengths of the two ecosystems. Nostr just isn't ready right now. It's annoying to use in a lot of ways. The only people who will stay are people who are okay with alpha software.