Yeah D&D is weird about that, and it's been a discussed and addressed problem since 2nd edition at the latest.
D&D, for some reason, which I think runs against how most groups want it, wants you to go through various magical weapons, and definitely not start with one, which becomes stronger (Pact of the Blade is closest).
But all the way back to the late '80s, you find a lot of people who would rather get one magic weapon that grows with them, and really says something about their character and so on. This is vastly more common in fiction - the number of heroes who go through multiple magic weapons is vanishingly small compared to the number who have a beloved magical weapon (often bequeathed to them as a child or teen).
And the first major-major attempt to "fix" D&D, Earthdawn (1993), marketed as a major feature the way you bonded with a magical item and it became stronger as you wove more of your spirit into it as you leveled up (sorry for run-on sentence). It's really weird that D&D doesn't "get" this. That is an actual "miss" of the kind you were discussing.