Season one episodes certainly seem to agree with your assessment. Pierce started out as just a clueless old white guy. For whatever reason, be it Chase himself or the writers, the character evolved into the asshat he is today.
This isn't always bad. Troy has also evolved away from originally conceived. Many other shows have this happen as well when certain actors begin to find their character's voice or when writers start writing to an actor's strength. Its worked for Jim Parsons on TBBT, and he's even parlayed that into some Emmy wins.
That's because Parsons is a very talented and smart actor. He has been able to keep the ultra obnoxious Sheldon as lovable/likable as ever.
Chevy on the other hand, I think, simply lacks the acting talent and smarts to simultaneously make Pierce a racist, homophobic, out of touch asshat, while keeping the character funny, relevant to the rest of the characters and the show, and most of all, likable.
You put the right actor in Chevy's place (read; an actor with real talent) and everyone suddenly loves the obnoxious racist, and very funny, Pierce, no matter how the character is written. As it is, many people otherwise devoted to the show, despise both Pierce and Chase.