We aren’t told what The Child Mando 20 this is the way shirt group calls themselves other than the Tribe, so let’s abbreviate that to a for his middle initial. The Child’s still a baby by appearances and actions, if not numerical age so let’s combine the letter with Mando. The child must be an infant. This makes it generally helpless, thus dependent on the Mandalorian and it also represents the Mandalorian’s own sense of lost innocence, as he himself was an orphan. It thus ties to the Mando’s motivations and themes in precise fashion, humanizing him and giving him a little life to protect in an otherwise morally bankrupt outer rim. Only the blank slate of an infant or toddler is suitable for this purpose.
The child must be so important to The Child Mando 20 this is the way shirt remnant that they are willing to shell out massive amounts of credits and spur every bounty hunter in the sector to go get it. Very few traits make the mass expenditure of life and resources pursuing one Mando and one baby make sense. Force-sensitivity is the big one, and perhaps the only one. Baby Yoda is not just an obnoxious internet meme. It is an incredibly elegant and precise storytelling choice. You will see few so perfect in one lifetime.