do you think lemmy will ever be popular?

Depends, it's been a bit disappointing to see virtually no change since I started using it, particularly in terms of QoL. It is open source, so that's on everyone, including me, but I had hoped for more speed, etc..

Mastodon is way better when it comes to filtering.

Having the option of a reddit clone is pretty good though and I will stick with it. Who knows when and where it will get that critical bit of momentum.

It's already superior to regular forums, in my opinion, so now the question is what kind of format you want to have discussions in, instead of having to default to forums. That choice is a definite upside and I'm glad it exists.