When was the last Metroid game that is "just as fun and joyful as the previous ones"? Metroid has had a tough 20 years or so. Last I checked Nintendo released a poorer version of a remake some fan released a year earlier.
It could also be because I got 'hooked' on Metroid because of Metroid Prime, and IIRC that one also was a bit more linear by virtue of the hint system.