Indeed....

No, it isn;t.
It is perplexingly simple, yes. But you're still quite wrong.
You do NOT decide what EV the scene calls for, you decide what EV CORRECT
EXPOSURE calls for.
And correct exposure depends on two things: the light level in the scene and
how much light the film needs.

Then apertures and shutterspeeds come into play (and then EVs too apear):
you need to chose a combination of aperture and shutterspeed that will
govern the amount of light present in the film permited to reach the film.
Set too long a speed or too large an aperture, and the ratio between light
levels both on film and in the scene will be wrong to get correct exposure.
And doing the reverse will have a similar, but inverse, effect on that
ratio.

So given a certain scene light level, and given a certain film speed, there
is only one ratio between the two that will produce correct exposure.
Since both aperture and shutterspeed govern that ratio, it is correct to say
that there is only one aperture-shutterspeed combination that will produce
the correct ratio, the correct exposure.
That combination is the EV that will produce *correct exposure*. The EV that
is appropriate for the scene and film, if you will.
Separate things, you see?

As we all know changing aperture and simultaneously changing shuterspeeds
inversly will keep the ratio between light levels on film and in the scene
constant, will keep correct exposure. And if the combination produces a
certain incorrect exposure, changing both this way will keep the magnitude
of the fault constant.
So (as we all know too) there is not just one aperture-shutterspeed
combination that will produce correct exposure/the correct ratio, but many.
And consequently a certain EV value does not just indicate one such
combination, but all that produce equivalent exposure, all produce the same
ratio (and this is quite independent (!!!) of whether or not this
exposure/ratio will produce the desired/correct exposure for the light level
in the scene and film speed used!). So all are given the same EV value.

That's the entire reason EV values exist: as a simple shorthand notation for
many aperture-shutterspeed combinations.

So understand this, and remember it forever: There are no light levels nor
ISO values in EV, just shutterspeeds and apertures.

That's not a matter of complicating things. It's a matter of what you (and
others ) are saying just being very incorrect. And that while, as you too
mention, it is all so simple.

Be careful, since this kind of thing is exactly why people are so cinfused
about EV.
What you can calculate is "what EV is suitable" given a certain light level
and film speed.

Its like formulas calculating how long a pice of string should be given two
other entities that requie a piece of string of certain length.
While people will never believe that the unit of length is defined by these
other two entities, the somehow do believe that EV is defined by those two
other entities in such calculations.
The reason why they do so is very hard to fathom. But, as we see here too,
they'll jumpt at ny opportunity to demonstrate they do.

So again, be careful. Always explain that what you are calculating is not
what EV is, but what the magnitude in EV of another entity must be to
satisfy the demands set by some goal (in this case correct exposure),
depending on other entities, light level and film speed, as well.

And it has nothing to do with either film speed or light levels, yes.