Max Stassi is obviously significantly better as a starter, and Romine isn't quite head and shoulders better than the rest of the organizational depth at the position. Sam Blum of The Athletic laid out what that depth looks like:
And Angels fans know that Kurt Suzuki won't be getting DFA'd anytime soon. Angels GM Perry Minasian loves Suzuki, despite his awful play with the Angels. Since arriving in Anaheim last year, Suzuki has batted .217/.289/.333 (.622 OPS) with a 72 OPS+. Those are all career-lows.
Austin Romine didn't get the job done with the LA Angels in limited opportunities.
In Austin Romine's eight at-bats with the LA Angels this season, he batted .250/.250/.250 (.500 OPS) with a 46 OPS+. He unfortunately did not drive in any runs or score any. He struggled in Triple-A as well, hitting just .273/.368/.394 (.762 OPS) in 10 games at Salt Lake.
Those AAA statsitics are solid numbers for a catcher when in the Big Leagues, but they leave a bit more to be desired against Triple-A pitching. Thaiss and Wallach are intriguing talents, but they don't have the best track records with the bats either in the Big Leagues.
Wallach has a lifetime .200/.265/.300 (.565 OPS) slash line in his six years in the Bigs. Thaiss' lifetime slash line is better, but not exactly impressive at .200/.289/.394 (.684 OPS) in three years. The bright side, however, is that those two aren't old yet. Wallach is just 30, and Thaiss is just 27.
Romine, on the other hand, is 33. He's no dinosaur in this game yet, but those few years of more wear and tear on his body are going to have the Halos prioritizing younger players for catching depth. Suzuki is unfortunately held to a different standard, but hopefully one of Thaiss/Wallach will pop soon and Angel fans won't need to see much of Suzuki going forward.