In some ways, Nightmare of the Wolf suffers from not being a TV series. It doesn't need to have multiple seasons, but a limited run, similar to something like Arcane, could have woven together a compelling and subtly different look into the origins of the Witchers that we now know and love. Cramming Vesemir's entire back story into a plot that also includes the downfall of the School of the Wolf, a plot about mutagenic magic being misused, and an intriguing half-elf hybrid meant that few parts had the space to really breathe.
That said, I also understand that this is distinctly the point. NotW is supposed to be a snapshot into the time before Geralt's Witching days, when Witchers were more plentiful and the world was growing increasingly less kind towards them. We don't need deep character arcs or a particularly varied cast to achieve that, and getting to see Vesemir in his prime is good fun. Plus, the film does do Vesemir's own character development well and I genuinely enjoyed the twist return of his lost childhood love, serving as a humanising moment for him. In that way, it's neat enough and gets the points across that it needs to.
Throw in some excellent action sequences and some genuinely unique and novel moments, as well as plenty of the atmosphere that makes the games so compelling, and the result is pretty entertaining. The voice acting could have definitely used some refinement, particularly with the younger characters, whose faux-English accents feel like an AI attempting to recreate Oliver Twist, and there were a few moments that the plot left me a little lost as to what was happening, even with fairly exposition-heavy and clunky dialogue. But overall, it's a fun romp with some solid worldbuilding that offers a slightly unique angle into the world of the Witchers.