But is that really true?

What I mean is, for controlling the timeline and being able to reset any reality to have any personal meaning, you have to be part of that timeline and reality. Otherwise it's just something else; as with the TVA we've seen so far, they're just doing a job. They're outside the timelines and realities, and for the most part they appear to have no personal connection to them (souvenirs and a liking for jetskis aside).

But for someone who is part of a particular timeline and reality and wishes to continue to be so, they'd still be subject to the infinity stones of that reality; those would still be all-powerful within that reality.

So while in principle someone from a particular reality could use the power of the TVA to make the 'sacred timeline' to their own personal preferences, ensuring that the infinity stones within that reality are only used according to their desires (in theory... it's worth asking, say, whether had Thanos in possession of the infinity gauntlet been deemed to be a variant, the TVA could have stopped him, given that once in his reality they'd have been subject to his power?).

And even if they could, would that still be real and have personal meaning, or would it become meaningless through how it was created?