Very true, I've seen plenty of power-trios covering 9/10 piece band tunes, missing all the important hooks etc, with nobody knowing the form, drummer picking feels at random, and people still come up and say the band was great.I think it depends on what kind of music you play. If you're doing avant-garde jazz you're audience is likely to be a little more sophisticated. If you play bars and dance clubs chances are your audience wants to drink and dance and thinks a high hat is something you wear on your head after you smoke pot. An audience that has ears that work will be able to tell when a band is really, really bad...but the band would have to be exceptionally awful. I've seen lots of bands that get a great reception that I would classify as crap. If the singer is singing the correct vocal line, the band is in tune and the music sounds sort of like the way it does on the radio, that's usually good enough.
Ok.... so I've occasionally been IN said power trios (if you say YES to any gig which pays well, you win some, you lose some
I would not consider the other people in that trio (or the members of other such groups I've seen) pro - and I wouldn't expect them to get any substantial bookings outside of dive bars/pubs.
I guess what I'm trying to point out is that while they get paid, they're not pro. A pro is adaptable, someone you wouldn't hesitate to book as a session guy or a teacher (as mentioned above). Either that, or, they're crap but they DO play massive venues constantly (i.e., they're in a super famous rock band, the success of which wasn't dependent on their skill). Which leads me back to: Pros do it for a living. Not just get paid, but get paid enough that they don't have to do anything else.
I hope this doesn't offend anybody who does do other stuff in their life! I would consider myself pro, but I have a day job (somewhat music related... distantly). But, I have lived solely off music, and I think a pro is someone who has (or at least feasibly could) "do" music for a living (incl. teaching, production, writing as well as playing).