Usernames are important. Various sites have different ideas of the significance and weight of a username, but I take people at their word that the name they have chosen means something about themself. It might not be a literal meaning, but it's information.
I also remember usernames - when I was actively playing League of Legends, I would semi-regularly encounter players whose names I had seen before, and sometimes recall the champions they played, and sometimes hints of how they played and fragments of what they said in chat.
I get that on social platforms that people visit on and off for many years, usernames may not reflect the changes in people's personality, so this accounts for variation on different platforms.
I personally spend a lot of time on usernames - I've had many through the years, and still struggle to represent myself succinctly. It has always felt like a suffocatingly weighty choice. If I had to choose one word or phrase that everyone I met would read, what would it be? What one thought would I like someone to have? Humans are complicated, and I have a lot of interests and traits to speak up about. I still don't have a username that I feel is helpful. In exactly the same way, I'd like to have an artist name for my music/games that isn't just my real name, particularly since someone else beat me to the punch.
Sometimes I go just by Axel, and that tends to do the trick for me, but it's not easy to grab that name - I only got it for audio.com. Still, it's not a terribly common name, so if I was to make a go of a music performance career, I could try for it.
I have username ideas every once in a while, and I'll try to remember to put them here when I do. They'll probably mostly be wordplay, and I'll try to keep it to things with 0 results on Google. Just the one right now.
Let me know if you want one I have listed here, and I'll take it off the list.