That would mean that your assumption that it's some black magic difficult process is correct. It's really not. Innodb has been the default for years. A little experience and it works fine. I've been doing it for many years on far bigger databases. At some point you want to look at storage speed and make sure you are on the correct hardware but MySql tuning is not difficult. MySql is also free. A lot of boards would not exist if they had to pay for a SQL server or Oracle license
Interbase was free in 1997 or '98 when I needed an SQL server on windows. (On not windows postgres existed since forever.) And if work had a delphi license, it came with a database abstraction layer with more features than any of the ones that exist now, and you didn't need to tie your code to a particular database product at all. Of course, all the k3wl kidz at the time were h4x0ring linux kernel and/or coding non-rectilinear 3D game graphics, and didn't write BBS software much. On the bright side, with BBS there's more choices than just "WordPress or WordPress", so there's that.