Hmmm…

The starting point of only 12 keys is highly objectionable, although I have to honestly admit that, ultimately, it is indeed a matter of viewpoint.

The very notion of “key” is highly dependent on the form of music theory that evolved during the Common Practice era. There are undoubtedly 12 different “notes” (or pitch classes, to be more accurate) and during the Common Practice era (roughly from the Baroque period to the Romantic period), it was considered that each note could be the tonic of two modes: the major mode and the minor mode. That makes 24 keys, not 12.

In fact, there are even more keys.
– there is one major key without sharps or flats and one minor key without sharps or flats
– there are seven major keys with up to seven sharps and seven minor keys with up to seven sharps
– there are seven minor keys with up to seven flats and seven minor keys with up to seven flats
The grand total is 30 engraveable keys. But that total includes enharmonic spellings. Most musicians discard them and stick with the 24 keys mentioned earlier.
Bach, Mozart and others have all composed “demos” in all 24 keys – that’s not a coincidence.

It is quite possible to make music without the notion of keys, or to give another definition of what a key is. But that’s not how a key is normally defined, and in the long run it tends to be very confusing.
Moreover, it very quickly leads to a terrible definition of what a mode is.

So, you are welcome to adopt the “only 12 keys” viewpoint if you want to, but I certainly don’t recommend it.