Batman: TAS is my favorite of the DC cartoons, and probably the best superhero cartoon ever. That said, its art style when it switched to a more Superman: TAS style was a big downgrade in quality. The style worked for Superman, but made everything look way too cheerful in batman, and made it more unrealistic. .
Everything you've said is correct. Anybody who disagrees is wrong. Now I don't have to chime in with my own opinion.