I understand the problems with scaling fluids and things that act like fluid like moving sand.
My take is, if an effect is not able to be done without breaking the tonal illusion of reality it should be left out.
The shots of the water shooting through the mine shafts weren't that bad at all.
The establishing matte painting was really good, the shots of the actors responding to real water were good too so it would have been better just not to show the fluffed shot of the water gushing out if they couldn't bring it up to the same level as the rest of the footage.
ROTJ is also cursed by inconsistent effects work, one example the heroes talking on the moving skiff with barge behind them looks awful compared to the stationary one.
If they had manipulated footage shot on location instead of using models and studio footage it might have looked better but it might have been best to have adjusted the script so the actors delivered the lines when the barge and skiff were still or cut the lines altogether.
The low budget television shows of my youth got away with terrible special effects compared to big budget films because they had a consistent look so they weren't questioned just as you wouldn't question the enclosed physicality of a theatrical play or a puppet show.
The effects in Raiders match up pretty well with the action sequences and stunts in that film.
If they didn't it would wreck the work of all the other people on the production in the same way that a terrible script or a wooden performance would in a film with amazing special effects and sets.