My main push on the bolded is games and teammates go out of their way to punish experimentation once you hit a certain threshold. I have a 2nd Valorant account to play with friends that have a horrible time if they queue up and play around my Elo. I had this happen in Dota 2 a lot actually, new hero is released and I want to try it. Gave it a solid week to get used to it(I think it was ember spirit this time) and that was quite frankly the most toxic week of gaming I ever experienced and was genuinely reported for "throwing" pretty much every game for one or two missed opportunities as I got used to him."Easy kills" means you don't want a fair game, you want to win. Which is very human, but stems from insecurity and hamstrings your learning, given you learn more by losing than by winning.
"Experimentation" is something you can do on your main account. If you care about your ranking so much that you find the idea of it dropping down temporarily due to a few losses, there's no other word to describe that but insecure.
That said, we're all insecure in some or other way, and insecurity about a videogame is a rather harmless thing in the grand scheme of things. "Insecure" is not the insult a lot of people seem to think it is; it's only when that insecurity becomes obsessive and crippling that it becomes a problem.
Overwatch has done a much better job at dealing with this by giving you 3 separate queues/ranking so if I'm trying to play DPS for a week, I don't fall into wildly disproportionate skill level games because my tank rating is as high as it is.
Having alt accounts does not strictly come down to some form of insecurity.