Implement the scaling tech on all old raids so we can go do them as they were meant to be done.
Give Artifact Power per boss. There, incentive.
EDIT:
I never said they had to force the scaling, just have it as an option for people who want to do it. Give Artifact Power and maybe some other incentives for doing it.
Also doesn't have to be all raids, maybe just give the option for a few favourites, gauge reaction and bring more in the future. That way, the ones that require more tuning can be released one at a time in the future.