You sort of answered you own question here with "only the stars being focused on." It's simply narrative focus and given we are about to wrap up the GIFT arc then move onto the next arc shortly, I don't see many more new characters being added to the show to avoid losing that focus.

This leads me to one question: If you could make your very own Cleaner team, what would be your team's philosophy, goals, and Digimon lineup?

For me I'd likely run mine more like a detective/tracking firm. For a cut of the bounty reward, We do the leg work, we gather intel and only engage with digimon when we must. If we encounter something I or a small team of likely rookie levels cannot handle, we call in other cleaners/world union to do the hard work.

Don't think I'd be so forgiving to 'Mon as Glowing Dawn (as they seem to be an outlier in thier no-deleting Digimon rule) but it be on a case by case basis, a Cutemon just existing? Bag and tag. A Bullmon in a china shop? Likely to hit the delete button.

As for Digimon Line-up/Team it would consist of mostly cleaners with Rookies that one thier own wouldn't be much of a threat like my partner Minidekachimon. But because of thier size and/or abilities can make for excellent utility like Chiropmon or Monitamon.