That's why after trying out a few distros back in the day I settled with a rolling release one and truly learned linux.

I totally agree with the "uselessness" of too many distros but not with your conclusion.

There are multiple reasons for linux not being Mainstream on the desktop.

Windows comes preinstalled on 99% of all non self built laptops/desktops.

Installing an OS is not something the average user does.

It's different and people hate change, unless it's popular