I agree, like the way Rick Wakeman used it on David Bowie's Space Oddity, and later with Yes. Wakeman talked about how difficult it was to keep the Mellotron working though. It's probably not the kind of instrument that does well traveling from gig to gig.
The Moody Blues were pioneers with it. Their guy could keep it working.
That would be Mike Pinder. There’s a YT interview where he describes one of the band’s early shows in, IIRC NYC, when the mellotron literally went to pieces right before the show. The audience waited patiently for over an hour while Mike put it back together and got the thing working again.