If you don't want to call up Morel unless he's gonna play a lot, then I think I agree with Ross.
With Mervis' call-up, there's not going to be many 1B or DH at bats available, doubly so with Mancini coming out of his early April struggle and looking like an above average bat we expected.
Hoerner and Swanson are gonna play basically every day, while they may require a rest day on occasion(Nico more than Dansby), it's not something that will happen every week that you can bank on Morel being able to get regular PT that way.
Bellinger is playing too well to not play every day in CF, and even if you want to shield him against LHP, Velazquez is probably just as good an option and that represents his likely future and he's already on the roster.
Which leaves 3B, where Morel has the paradox of being too similar to Wisdom in profile. For as much as people groan at Madrigal's playing time, he's being used in a specific, almost sacrificial way. As a crude example, per BR Madrigal has had only 30% of his PA come against "Finesse" pitchers, compared to 43% for Nico(who serves as a team baseline) and 45% for Wisdom. The playing time Madrigal gets are the worst matchups to throw Morel into, otherwise we'd have just given them to Wisdom while he was hitting like peak Bryant. So until Morel demonstrates contact ability that he probably never will(his K rate in AAA is 29%), or Wisdom falls into a deep enough slump that you consider Morel a superior every day 3B option, Morel is kinda stuck unless an injury shakes things loose.