Don't bother convincing. 99.9% of people prefer rubber domes. The rest 0.1% are geekhackers.
I don't think that's true. 99.9% don't know any better. I wouldn't expect everyone to fall in love with mech boards though. Some people will truly prefer RD keyboards. In many cases, you can't appreciate mechanicals unless you give yourself time to acclimate.
I know that decades ago, I hated model Ms and model Fs. I didn't own one, and I was always on a computer that didn't belong to me when I was using it. The touch didn't appeal to me whatsoever. Now a model M is my daily driver at work (for now). I came to appreciate what was good about the model M, actually owned one, and gave it time.
I know that I did always like my Amiga keyboard but sometimes felt it was a little tiring. Guess what? PCB-mounted Cherry MX blacks w/ doubleshots... I also thought some WYSE terminal keyboards I found myself using (WY99GT mostly) were really great once I got used to them. MX Blacks again. On the other hand, VT220 keyboards sucked large. No idea what's in those.
I got into MS Natural keyboards for a while. I found one or two around the office that didn't have a lot of off-axis binding and liked them, but struggled with off-axis binding in a lot of boards I used. I wondered why my Amiga keyboard didn't do that. Now I know, but back then I didn't.
When I got my first Cherry Brown board, I was a little unimpressed. The brown switch lacked the tactility I was expecting and felt gritty. If I hadn't been studying at GH in advance and someone plopped one in my lap, I don't know that I would have been impressed. The benefits have grown on me and I've become accustomed to the touch. I'd still like to try ergo clears sometime. I LOVE the Realforce touch. The 55g felt awesome, but had a hard time getting up to full typing speed on it so I sold it. I have a variable weight in the mail. Of course, the RF is just very very good rubber domes.
The biggest thing that bugs me is off-axis binding. Especially variable, unpredictable binding. Both Realforce rubber dome and Cherry MX handle this very well. Cherry ML is mechanical too, but binds a lot in my opinion. I've tried a couple of ALPS boards that still seem to bind so they are unattractive to me. One of the greatest things I notice about my model M is smooth, bind-free operation despite the heavy key weighting.
So - does it matter what everyone thinks? Should everyone mindlessly love any mechanical board you toss at them after a 2 minute test drive? I don't think those are reasonable expectations.