Why are there so few UQ Holder doujins?

[Gunblade]

I've always thought Ken Akamatsu's stuff was great doujin fodder material. His previous stuff definitely has no end of them, but UQ holder, you can literally count time on your fingers. Less than 10 when I checked.
Was it not popular enough?
It certainly had some nice looking characters.

 

[Kri]

Basically the times have changed.

Back then there would be more doujins about popular mangas / series, but nowadays gachas have replicated those.

In short most of doujin creators are switched to the FGO, Blue archive etc unlike old days were they care about the other medias as well.

 

[Gunblade]

Basically the times have changed.

Back then there would be more doujins about popular mangas / series, but nowadays gachas have replicated those.

In short most of doujin creators are switched to the FGO, Blue archive etc unlike old days were they care about the other medias as well.

They have but you can defo find doujins on other popular manga series also, granted as you said reduced in number than what we use to see.
Still in far greater quantity than UQ Holder though and I saw that series as a big hit.