First things first, the answer to the question is Betteridge's Law. But if you wanted to make the bull case for Mastrobuoni as a player:
He's pretty consistently hit at a good level at AAA, a 122 wRC+ over 1000 PA, with 13%/19% BB/K. The plate discipline in particular separates him from Madrigals of the world among contact/low-power bats. ZiPS seems to think that translates okay, they estimate him for a 93 wRC+, which if you combine with slightly above average defense is pretty close to a league average play. He also adds value on the bases, across AAA and MLB he's 55/64 in SB.
But I wouldn't put money on the ZiPS forecast, as his lack of power is probably going to lead to pitchers more fearlessly pounding the zone and make him more at the whims of the BABIP gods. Plus as a *regular* his profile is not one the Cubs can afford in a lineup that has Hoerner and probably PCA(to say nothing of the catchers). He is however, a decent bench fit, as there is no 150 game 3B on the roster, and he's the only LHH for 2B/SS/3B on the 40 man unless you stretch Busch, and no other internal options appear imminent(Shaw, Triantos, & Vazquez are all RHH).
As it stands, he's perfectly fine as a 26th man option you can yo-yo to Iowa through next year. If he starts living up to that ZiPS line and there's opportunity you can give him more platoon sided bats, but the best case scenario is that he's written in pencil on the 26 man roster for 2025 similar to Tauchman in security(but not in quantity of playing time), there's just not a path to being more than that unless there was an overhaul of the roster that won't and shouldn't happen.