I think that both player selection and the quality of play in the All Star Game has improved noticeably in the 21st century.
The quality of play in the late 90's and early 2000's was frankly atrocious, and it improved after the game was tied to World Series home field. Changing that rule has not yet led to a deterioration back to 2002 standards. Fans have gotten much smarter about who to send to the ASG. Back in the early 2000's, it was more common for fans to simply vote for the players on their favorite team, which led to a lot of mediocre Yankees, Red Sox, and Cubs on the team. Today those teams still receive outsize vote share, but voters are willing to elect a guy from Kansas City, Arizona, or Washington if he's really good.
But to me, quality of play is a decision factor in whether or not I would watch the game on TV. For in person attendance, the factor is 99% that the All Star Game happens in my city once in a generation and 1% everything else.