The whole point was that all the main characters were stereotypical nerds and each displayed a different type social difficulty. I mean Sheldon was obviously supposed to be somewhere on the autistic spectrum, how is that not ableist or whatever?
It was also apart of his character arc! If you watch the show, Raj eventually overcomes his fear of talking to women and ends up dating multiple women (sometimes at the same time) later in the show.
There are a ton of jewish stereotypes present in the show as well, but they are hilarious, and > 50% of the cast is jewish (as well as almost all of the producers AND the director), and obviously they were not offended and CHOSE to write and direct the show that way. My point being, it's just comedy and if you actually watch the whole thing, it has a good message.