"the different engines provided are for different tasks"
You should think of them more like separate DBMSs that are tied together in one system. The semantics change depending on the storage engine, so they aren't just drop-in replacements.
"MyISAM for example supports fulltext indexes..."
PostgreSQL has supported full text search for a long time.
I didn't claim they are drop in replacements, just like I wouldn't claim you can just jump from MySQL to PostgreSQL.
What I said was you need to do your research and pick the right tool for the job.
I haven't used PostgreSQL for quite a few years but I think it got built-in support for fulltext indexes in v8.3 (April 2008) whereas MySQL had them in v3.23 (April 2001).
A lot of shared hosting providers/package management systems wouldn't have supported/installed the extra extensions to make PostgreSQL support fulltext indexing prior to it being built-in I suspect.
To be clear, I don't care what you or anyone else uses - I was simply pointing out that just because it was the default engine it didn't mean you had to use it!
For what it's worth, AFAIK there is no reason other than development effort, for InnoDB not to have full text search. I am sure it will get it eventually.
You should think of them more like separate DBMSs that are tied together in one system. The semantics change depending on the storage engine, so they aren't just drop-in replacements.
"MyISAM for example supports fulltext indexes..."
PostgreSQL has supported full text search for a long time.