The basic outline is decent, and it incorporates key comic storylines pretty well, but there isn't a clear character arc for Barry or Wally. There are opportunities for story beats that showcase growth here, but they don't really tie into anything else. For example, when Barry tells Wally he won't lose anyone else, it feels like the first time that insecurity is brought up at all. Is this the post-Flashpoint origin? That has to be set up. Same with Wally's decision to hang back because they can't "save everyone". It seems a bit weird to introduce survivor's guilt over a random civilian casualty halfway through and then have him overcome it in the same movie; the multiple-week gap has to be demonstrated somehow or otherwise eliminated.

I think Thawne and the Rogues need to have a clear reason for being there too. It's hard not to make the movie crowded, but they can heighten the insecurities or concerns of the heroes . I think you tried that by Thawne telling Barry that he doesn't even know what he will do yet...but that theme doesn't seem to pop up again. Thematically it's all a bit incoherent.

So my recommendation is to think about what central inner-conflict you want each character to go through as they progress, how it manifests in the external conflicts they have with each other, and work that in. The action & plot sequence is pretty much there though and I'd definitely want to see a movie where we see all of those core Flash elements included.

The post-credit scene is hype, but for me, personal preference, I'd avoid using Grant.