Rixey pitched for the Philadelphia Phillies from 1912-1917, 1919 and the Cincinnati Reds from 1920-1933. His call into the Hall had much to do with his longevity and less to do with his dominance during the time he pitched. He finished his career with a 266-251 record, 3.15 ERA and a 1.272 WHIP for his career. The time he pitched coincided with the change from the dead ball era to the live ball era. Though he was consistent throughout the change, he still was never a top pitcher in the National League. Though Rixey was a four time 20 game winner (1916, 1922, 1923, 1925), a case can be made that those were his only above average seasons. The 251 games he lost are a MLB record for a LHP.
On the positive side, Rixey did adjust very well to the change in the game. He managed to give up few home runs in spite of the increase in offensive output. Prior to the live ball era, he pitched for the Philadelphia Phillies when they won the NL Pennant in 1915, a World Series they lost to the Boston Red Sox. Rixey also fielded his position very well, five years finishing the entire season without making an error.
The fact that Rixey is in the Hall of Fame is to me, neither here nor there. I do think more thought needs to be put into why pitchers such as Jim Kaat and Tommy John and eventually Andy Pettitte, will likely not make it into Baseball's Hall of Fame. Kaat finished his career at 283-237, 3.45 with 1.259 WHIP. John finished at 288-231, 3.34, 1.285. John had a .555 winning percentage, Kaat was .544, but Rixey was at just .515. Pettitte finished his career with a 253-136 record, a .626 winning percentage. Even Jamie Moyer finished with a 269-209 record, good enough for a .563 win%. Perhaps your concluding thought could be that Kaat, John, Pettitte and Moyer should be in the Hall of Fame because Rixey is. I will not go to that level, as Pettitte has admitted using performance enhancing drugs and Moyer was never very dominant. I do think Kaat is a Hall of Famer, and would not object to John getting his day. It looks to me that the BBWAA and the Veterans Committee honored Rixey more for pitching 21 MLB seasons than being one of the best in the game. If that is the case, then should John be put in because of his 26 seasons and Moyer and Kaat be put in just because they pitched 25 seasons? Longevity is a great feat, but not one that should inshrine one among the greatest to ever play this game.