Aight, this bit needs it's on section bc ye... here comes the productive, instructional ranting like I've never ranted before.
Just because your book contains Magic or is fiction DOES NOT give you the excuse to toss logic out the window.
The more illogical something is, the more plot holes will crop up over time. It's as simple as that.
Now for the examples... Let's take mana based magic and say a country has the means to look at things microscopically (on par with early microscopes).
Background: In our timeline, microscopes were invented around 1600 and early telescopes around 1608. You don't have to make the years exact, the flow just needs to be logical (more on that at the end).
This magic circle/array setup was invented in say... 1551 since the convenience of magic helped speed some things up.
Telescopes should then be invented a year later, two max. SINCE IT'S THE SAME TECHNOLOGY AS MICROSCOPES (sorry for caps, there's no italics).
This also works vice versa, if telescopes were made first, microscopes should be invented shortly after.
Now let's say the author completely disregards microscopes... Needless to say, having the discovery of microscopes being more than 2 years after telescopes is already illogical bc telescopes are just general purpose microscopes.
With the invention of microscopes comes the theories of cells, bacteria, pathogens, all that good stuff. In our timeline, this took about 7 decades since the microscope technology needed to catch up to actually see cells and bacteria. Yes, different zoom settings exist for microscopes.
With the convenience of magic, i.e. fine tuning settings on arrays and magic circles instead of making a completely new microscope and lenses for each zoom, 7 decades could be shortened to a decade max. Really the only limitation here is the mage's power and knowledge so yeet the tower master in there and problem solved. sort of.
Aight, now for the plot holes...
If the writer completely disregards the inventions of microscopes, and just says "The peeps here have had access to telescope-like magic for 3 decades" but no knowledge of cells, bacteria, plagues, etc. is even hinted, then that's a plot hole.
Right now it's only evident for those with a discerning eye, but it'll become extremely evident when a plague happens and the entire populace, including the mages and the royal peeps, are completely clueless as to how it's spreading, how to prevent it, etc.
Not even a magic plague or airbone one, just a vanilla plague transmitted through bodily fluids (So medieval covid).
Ay, if you just thought "Well the problem is solved if it's a magic plague." go have your snacks confiscated.
So let's say it's a magic plague... How is it magical? Does it attack the mana of people? Then what about those without mana? Wouldn't this targeted plague give mages more incentive to find out how it's spread and how it's caused?
So ye, logic applies to everything. Just because it's logical doesn't mean it needs to be realistic. Most people accept fire magic + earth magic = magma magic because it's logical, even though it's not present in reality.
Another thing is that it heavily affects the reader's immersion.
Let's take video games and writing for comparison. If a corpse starts ragdolling itself into the skybox in a video game the player usually laughs hysterically. If the same thing happened in a novel, the reader will be confused, frustrated, annoyed, or even pissed.
But why? It's the same event so why do people react differently?
The difference relies in the method of immersion. In video games, you are controlling a player that has an effect on the world. How big of an effect is dependent on you (and sometimes the game's capability).
There is almost no greater immersion than that. Full Immersive VRMMORPG that you see in novels for instance, is this basic immersion applied to all of your senses instead of just sight and hearing.
For novels, you're just observing. That's it. You have no impact on the story, you don't decide anything, you're just witnessing it unfold. You have no control, you have no one to claim "yeah, that's my character. I blew up a few villages with it."
The latter has a very, very thin film of separation (often called the suspension of disbelief) that blocks the impact of illogical events on the reader's experience. For video games, that film is more like a wall.
To put it simply, the difference in each method of immersion affects how much one will accept illogical events happening. Since that barrier is tiny for novels, it's best to keep the boi as logical as possible to prevent ruining the immersion for readers.
And the best part about this? It affects all readers. Regardless if their method of reading is wish fulfillment, self insert, or something completely different.
Y'all can skip next chapter if you want, it's just me explaining the intricacies and misconceptions of fantasy and reality. It's focused on the saying "There's a clear line separating fantasy and reality." (TL;DR: of that chap is: there's no such line, it's just a matter of how much one is willing to blur it without confusing reality for fiction.)