But remember, Green acid is normal. It’s the barbarian fighting off the guards with a brick that is unrealistic.
Having actually been hit by a brick before, I can confirm that the fight scene was incredibly realistic...
Only NERDS care about Realmslore man

nobody cares if its canon or not, nor about Spell Levels. Nobody's gonna be counting spell slots in this movie.
Besides, DnD doesn't even let you interrupt spells anymore, you have to resolve them before your character can react, so it's already nonsense rules before we get to spell level. The character is using magic to protect an ally from a different spell, that's cool looking and that's all that matters.
The thing about experiencing something through a visual medium, rather than through a text medium (which is what the game mechanics of D&D are), is that words on a page have
never been able to translate directly to pictures on a screen - nevermind in a fashion that's actually entertaining. Any adaption of something from one medium to another is going to require
some creative license to even at least somewhat accurately convey the general tone of the piece in question, nevermind trying to exactly recreate one specific element of it perfectly.
Visual mediums require visual (and audio) cues and effects to convey what's happening in the story. But what does being a Bard look like? How do you distinguish between a Wizard and a Sorcerer until some bit of exposition in the film explains it?
If you go through something like the spell lists, how many of the non-direct-damage spells lack a physical description of what the magic actually looks like while it's happening? What's the visual cue that someone failed their save against
Charm Person, that a person is under the effect of
See Invisibility, or as mentioned above, that they've successfully counter-spelled something?
Barbarian rage or reckless attack might be possible to portray roughly onscreen, but what does a wizard with a dagger attacking with advantage look like, so that you could recognize it onscreen? What does elven accuracy or the halflings lucky trait (or any forced reroll or simple mathematical adjustment to a gaming mechanic) look like in a movie?
Any time you go to see something translated from another medium into a movie or tv show, you have to acknowledge that there's going to be some accommodations made for the limits of the new medium.
For a movie trying to recreate an rpg, they have to go with
Rule of Cool over strict adherence to game mechanics in order to make the film more entertaining and sell more tickets.
Especially considering that the majority of the audience (at least if they want it to be financially successful)
isn't going to be someone familiar enough with the game's rules to stand up in the theatre and yell, "Hey, they can't do that!"...