This may be true from your perspective but won’t sway over many newbies / plebs who don’t have the knowledge (yet) or who simply do not have or want to take the time for self packaging.
And flatpak, snap and appimage tend to become the standard to get verified, tried and tested software hosted & supported by the official maintainers or the company behind the software.
Now to the personal part:
There was a time when I was motivated enough to get packages from user repos - I actually never was motivated enough to do self packaging so maybe I have missed something world changing - but I got so tired of having to figure out the missing “optional” dependencies that meant the software wasn’t working as expected and having to trust 3rd party maintainers when most stuff on flathub was “install & ready” and officially supported or at least hosted by a “verified” source. And maybe distro xyz has a mindblowing solution to all my problems but for the moment I am happy with what I have and not looking for yet another distrohopping and yet another point was whilst distrohopping it was soo easy that I could use the same install.sh containing all my favourite flatpak apps & the “applications” folder containing my favourite appimages no matter if I was on a Debian, RedHat, Arch, … based distribution.
My bad, I didn’t emphasize the Your-way-is-perfectly-fine-part at all and focused more on underlining how it doesn’t work for everyone which made it look like I was completely opposed to you.
I wanted to say that both ways, flatpak/snap/appimage and self packaging / user repos are perfectly fine in their ways. The first may be more targeted towards newbies and people who do not want to hassle around with dependencies and the latter is for the more experimental kind of person.
If it works for you and you are happy then there is no reason to change anything. Having the freedom to decide how our OS should be is what drove most of us to Linux in the first place.
In that regard I fully agree with you and especially with “Do what you want, this is just my personal preference.”