You're not wrong. But it's possible that the people here just haven't figured out trans-dimensional travel yet. And I have some experience with that already.

[He doesn't miss a beat with the flash of insight from Leo. Of course Leo is insightful. He's Leo, even when he's acting like a doofus. Generally, Donatello feels that all his brothers are intelligent, even Mikey; some of them just choose not to let people know how smart they are until they absolutely have to.]

I can do no brussel sprouts. But you're not living off pizza. [Donatello crosses his arms and flashes Leo a fond smile, but his tone brooks no argument.] And you should try meditating. It's good for you. Like proper training.

[Is Donatello going to bully his new little brother into training and meditating? Maybe.

(What do children need? Food, shelter, healthcare, exercise, social interaction. Food and shelter is taken care of. Healthcare, he can stand to build his first aid kit back up but he can handle most stuff. Exercise will have to be in training, social interaction... should he send Leo to school, now that he's human? Something to consider.)]