I can't tell you how many MySQL users I've worked with where 50% of their dev work was doing complex caching and denormalization to avoid joins.
Now, as a MySQL user, you're saying to yourself "joins are slow". Yes. In MySQL, joins are very, very slow.
I mean, you could write a book on all the things MySQL does in a fundamentally broken way. It's a very long list. Generally, MySQL fans have only ever used a single database system, MySQL, and they extrapolate that it's completely brain damaged behavior is somehow a characteristic of relational databases. This is not so.
To be blunt, if you think MySQL works beautifully, I mean, will you at least admit that at least 95% of your experience is with MySQL? Anyone who had ever used any of Oracle, Postgres or even SQLServer could ever say that with a straight face.
I develop data management systems and one area of my job is to work with existing solutions and develop import/export routines, so I can assure you have I have a lot of experience across the entire spectrum of RDBMS's.
The MOST interesting thing I've found with the systems I've worked with is the insane use of SQL. Quite frankly, most developers have little to no real idea what they are doing when it comes to SQL, which is evident when you look at the rise of "NoSQL".
If you are a good software developer you will develop good software no matter the language. If you are a good DBA you will write good SQL no matter the underlying database system.
If you have a nice normalized schema, you will need to do joins, sometimes involving multiple tables and joining to sub selects. With MySQL, this is just a disaster, so you can't have a nice normalized schema, or if you do, you have to stash data in a denormalized way somewhere.
I've written just as complicated joins with MySQL as I have Oracle, PostgreSQL, SQL Server etc etc all with very similar performance.
Can you provide/email me with some examples of what you are finding a "disaster" and I'll help find the flaws in the SQL or Schema, whichever it may be.
Zero benefit, really, do you have to be so insulting?