I agree that basic build quality is probably worse than a similarly priced BMW, Audi, etc.
I haven't had any quality issues with mine but I know if I started measuring panel gaps it won't measure up to others in the price range. Noise insulation at highway speeds, door closing sounds, etc. don't quite measure up with the price either.
Mostly I prefer the simplicity of the vehicle and drivetrain. Alternatives from other companies are getting more complex both in interior (3 touchscreens + buttons + weird electronic shifter knobs) and drivetrain (auto start/stop, hybrid, plugin hybrid, 48v mild hybrid, turbo + supercharger, etc.)
A basic standard un-complicated ICE setup is becoming obsolete due to emissions, fuel economy, and power targets.
The biggest change I would make to the Model 3 design is ditching the frameless windows and using normal door frames which are less complex (no need for the window to move each time you open a door) and easier to seal up.