That's common enough with movies based on television shows. The Studio is concerned that not everyone in the potential audience watched the movie, and can't be expected to know what happened on the show. It kind of wrecked the X-Files Movie, and made most of the Star Trek TNG movies feel like expensive one shot episodes. It didn't seem to affect the First Decade Marvel films, although the Disney Plus era would probably disagree.
I believe I once watched a short special that abridged the storylines of Neo Genesis Evangelion in preparation for the launch of "End of Evangelion," so you can understand the extremely dense plot of Eva without having to rewatch the 26 episodes of the series. I think that would be the best idea. Or just buy the broadcast rights, and re-air the series on Trio or Bravo or CNBC or whatever.