I don't think they can ignore continuity forever, especially when it comes to Alola. The series is a world tour and that means they will definitely be visiting Alola more than once. They just can't have any of the old SM characters to not show up at all in all the Alola episodes, given how SM is still pretty much 'fresh' since it was the series prior to PM2019, and it was made really clear that Ash grew really attached to Alola, as compared to all the other previous regions. He would definitely want to see all his old friends again if he returns, especially if more than once. Although, the random never-before-seen Alola COTDs are probably what's going to happen instead lol.