The "or you need to take away someone else’s pie" is the relevant part here

The 174 changes (and SALT changes, and some other stuff) were how TCJA got balanced and passed without a 60% majority. 50%+1 is enough to undo previously passed legislation that was also passed with 50%+1 in this case (handwaving - not exactly right, because the balancing point is a different time range, so the math might not work out exactly the same).

The Democratic party absolutely could have passed some legislation in 2021-2023 to undo a lot of TCJA with just a 50%+1 vote, if they cut other stuff to balance. They didn't do that though. In part because they had literally 50%+1 majority and couldn't lose a single vote in the Senate, and couldn't come to an internal agreement.