Thats fine. My opinion stems from my experience.You can have your opinion and I understand that you do not see Rumble products on gigs around you. Fair point.
For yourself and everyone else here, bass players can use WHATEVER they want on stage to hear themselves. I have seen hugely expensive gear on stage as well as some of the cheapest and most terrible sounding equipment I have ever tried. And guess what? That bass player typically dials in a great tone on stage and they sound good to the audience! Please don't shame others for using gear you do not like. In the end, bass players can send a multitude of different signals to the sound person and the gear on stage is ONLY for them. Do NOT forget that.
Lastly, one of my good bass buddies who has filled in for me 2x uses a Fender Rumble head and Rumble 410. Guess what? He makes it sound awesome! I can always hear him through the PA and he hears himself just fine on stage.
If I find one on an open jam, I'm going to use it.. Would prefer to take my chances there than with an Elf or TC ...