I'm not sayin MySQL is that bad, but I exclusively hear this kind of advice and anti-DB rhetoric from people running MySQL and MySQL only, who are complaining about scaling.
MySQL may be able to perform better, as I haven't done in depth tests I wouldn't know how far it can be stretched, but my point is that almost everyone complaining about the performance of the RDMS model seems to come from MySQL thinking that it represent the utmost limits of what relational databases can do, and that is quite sad.
Hm. Well, I agree with your observations. But maybe they're more willing to suggest alternatives because they haven't invested so much into learning an alternate system? You would expect someone who has, say, spent the last 15 years becoming an expert on DB2 to refrain - even subconciously - from questioning the very fundamentals his career is built on. MySQL users may not be advanced but at least they are unbiased.
MySQL is not that bad, no. With proper knowledge it can do a lot, and beyond its limits, capably configured, I am not sure any RDBMS can help. Facebook is not developing Cassandra because they can't afford Oracle.
I first used MySQL a decade ago... There are plenty of people who've fully invested their careers in it. Which is as sad as someone who thinks MS Access is the state of the art.
MySQL may be able to perform better, as I haven't done in depth tests I wouldn't know how far it can be stretched, but my point is that almost everyone complaining about the performance of the RDMS model seems to come from MySQL thinking that it represent the utmost limits of what relational databases can do, and that is quite sad.