There is no right way. Only grey ones that help relieve pain for the team.
> Refactors and rearchitecture are.
Yeah... if you have the cash and the people. Usually, mature codebases are driven by limited investment with proven business value, because the sweet VC money is no longer there (or never was, in some industries).
And the more you put in procrastination-encouraging half-solutions, the worse your code base gets.