Personally, I think they are making a mistake in going to smart device/app control only. Not to mention selling sets that don't come with any sort of controller whatever. There are lots of folks who will prefer using a physical remote. And with good reason. Using a smart device eliminates one of the senses--touch. For both practical and aesthetic reasons, touch is valuable and enjoyable for lots of folks. A simple example. I absolutely hate using my phone or tablet for writing. I'd rather dictate, which is far from perfect, but a lot better than trying to use a virtual keyboard. No one learns to keyboard on a virtual device. If I'm writing, I want a physical keyboard. Perhaps not a perfect analogy, but makes the point. Touch is sometimes important for both function and enjoyment. MTH is limiting their market unnecessarily by insisting that all future purchasers use a virtual device rather than a physical device.
Perhaps a simple DCS physical remote for basic functions (speed, direction, whistle, bell, couplers) would be possible? Akin to the LC+ Universal Remote but able to control more than three locos? If it could be sold for under $100, it would be a winner, I'd guess. And it would keep options open that some users will prefer. My prediction: after a few years of growing complaints they will do so simply to keep their market share stable or growing. That's what led to the Lionel Universal LC/LC+ Remote is my guess.