Tldr?

You want the truth? Reactions so far have been mixed — not disastrous, but not glowing either. Milly Alcock’s performance as Kara/Supergirl keeps being singled out as a major highlight. On the other hand, several sources mention that the action sequences don’t quite land — director Craig Gillespie doesn’t seem to have a full grasp on them — and that the main villain, Krem, feels underwhelming. Reports, from multiple screenings, do indicate Jason  Momoa’s Lobo making a strong impression, despite the limited screentime.

I agree. If the fight scenes don't quite work, but the story is solid, that's a clear win in my book.

It could however make the villain not work, which would make the overall story feel weaker.