I know what you mean. The spring reverb effect is OK at lower settings but once you bump it up to a "surfs up" level it's not the same as a spring reverb tank. That must be harder to do digitally than it seems because the digital one on my Bugera v5 is like that too. That one is fine too if you keep the setting too but once you bump it it's not all the crystal clean.
Personally I just started using the plate reverb on my 40xl because to my ears it actually sounds a little better. Or the other option would be to get a really good reverb pedal like a tc electronic which has numerous settings and see if you don't find one there that doesn't help the situation. I think their reverb and delay pedals are far better than Boss which is what the Cubes effects are modeled after.
IME nothing beats the old spring reverb tanks or they would all have been replaced by digital ones long ago. They can be finicky and prone to breaking but they still do what digital models seem to struggle with.
CS Nocaster; Nashcaster; Squier CVC; Squier CVC/FSR, Nashville Tele; MP Thinline; Lenti Cavalier Esquire; Epi ES339 Pro, Taylor 214ce-dlx; Roland Cube 40xl; Roland BC 60; Egnater Tweaker; Bugera v5; CV JBass; CV PBass; tc BG250 Bass Amp; Zoom B3 Preamp.