Magic exists in Middle Earth but casting spells is not what the LotRs is about.
Exactly, this is literally what I'm getting at. Casting spells is not what frieren is about either, the main conflict in frieren is not martial, its emotional.
Spell casting was always central to the plot and solving every problem with it builds up a narrative debt because we need to know what if anything will give Frieren a problem that she can't solve with magic missile.
Saying that you need to know how magic works because you need to know if anything will give frieren a problem is missing the point of the premise. For all intents and purposes frieren is saitama. The conflict is not whether or not she can oneshot the bad guy, its literally everything except that.
The problems in Frieren aren't martial problems that can be solved by force, they're indirect obstacles that you have to solve with actual understanding and are more about what you learn on the way.
Finding the flower field by following a squirrel, dealing with the senile old man, discovering the meaning of lotus ring meaning eternal love, replacing the lost son of a king and so on and so forth.
When you were watching one punch man, was the main thing on your mind "God, when are they gonna powerscale saitama? I need to know how his powers work so I know if he's in trouble." Obviously not, because that's not the conflict.
Its literally the same thing here, every single problem frieren faces is one that can't be solved with magic missle because none of her problems are martial.
It also is probably the cleanest way to introduce Serie to the series along with the many other character who (apparently, not currently reading the manga) come back later.
To go back to the LoTR example, imagine if Boromir had to enter a warrior exam for the party to be allowed to progress closer to mordor, and the exam is how legolas and aragorn were introduced. If you want to introduce important characters, there's a million ways to introduce characters organically instead of shotgunning them into a tournament partway into the story.
I think a more reasonable reckoning for the tournament part of the arc is 4 episodes, I don't consider "everyone is on the same team doing a dungeon crawl" and Serie doing interviews to be a tournament.
Its 10 episodes of them stuck in the same plotline and same location when nearly every other episode was part of the road trip dealing with a different issue each time. I don't think its an unfair assessment to lump the whole thing in a single basket.