The devices and capabilities are not the issue that have held, and will continue to hold, these back.
The game ecosystem and entire philosophy is what will keep these from being successful.
When 95%+ of all games on Android are stupid microtransaction whaling games why on earth would people want to buy dedicated handhelds?
Steam deck is successful because you can download and play actual real games not just microtransaction scheme games.
Emulation? Sure but if I already have a Steam deck or any other type of device to emulate on there is no reason to buy a dedicated Android handheld.
Until consumers have a GOOD REASON to buy a dedicated Android handheld they will continue to fail.