Is phpbb or Mybb still good, or should I look for paid ones?

[Paul]

@batman Said it all. There is nothing much to say here. But I will add that.

If you think that to run a successful forum it will need a shiny theme, mobile optimisation & other advanced features, then you cannot be more wrong.

A community which is stable and have good contributing members will run itself in any platform.

All these things are additional privileges.