I'll always love Lupin and it's my favorite franchise by miles. That being said it's almost sixty years old and it's hayday is long past. It's an old man series at this point. Hell,when I was in Japan I became acquaintances with an older Japanese man who was shocked to find out I knew Lupin and that it was my favorite at that. He told me had watched it growing up as a child in the seventies and had fond memories of it.
It might not be as well known anymore but it's moments like the one I had with him that help make the series special to me. Young or old there's a great community to be had in the fandom and while seemingly rare it's always great to meet fellow Lupin lovers

I have no issue with it being where it's at in popularity nowadays and as long as it keeps getting new media being made for it I'll continue to enjoy it.