Not at the Federal level. No. The Constitution has specific age requirements for certain things like voting, holding offices, and for labor. Those would require changing the Constitutiton to amend. As for the States, it should be up to the people of each State to enact such legislation.
As for the Age of Majority itself. It is a logical enough legal fiction. I have no problems with it being set at the State level. Better yet would be setting up a testable metric for it. People do mature at different rates, but you really do need to have quite a bit of experience under your belt before getting "kicked out of the next" so to speak. Some may never quite gain that ability. Regretable, but it happens.
Then your answer is yes. you support the implementation of a government controlled legal age of majority whereby certain citizens, based on an arbitrary age, are denied by the government from engaging in activites that are legal for a certain class of citizens only because they have reached that arbitrary age.
However you did expand that it would be better to have a 'testable metric' for adulthood but that would be a whole other discussion so I won't diverge at this time.