I think it's worth keeping in mind he's the fourth youngest regular at AAA this year, and also the fourth youngest player to get a single MLB AB this year. If he were an american college kid he would be in next month's draft.
Given how heavily much the Cubs weight the between the ears aspects of catching, it's not surprising he got passed over. The only two catchers this century to get significant MLB playing time at age 21 or younger are Brian McCann and Francisco Alvarez. And the 2023 Mets sucked.
I will say it's not crazy to have other guys 1st. Mo's pretty clearly got the least power of the big four bats at Iowa. And while his age implies oodles of untapped upside, at 5'8" that remaining upside might in reality be pretty limited. I think if you promised me he wouldn't be able to catch in the big leagues I'd rank him somewhere in the 4-6 range.