In practice, in mostly countries that use STV PR, you have smaller electoral districts, for this reason. For instance, in Ireland, electoral districts elect 3-5 TDs depending on population. This is big enough to make gerrymandering difficult and not very effective, but small enough to avoid the situation where someone has to cast 53 different votes. And 53 would be the low end here, really. That would assume you only want to vote for one candidate per seat, which is not typically the way it works out. I'm in a four seat constituency and voted about ten preferences in the last election, say.

In practice, in STV PR it is generally optimal to vote for almost everyone on the ballot; you give low preferences to people you don't care about to avoid people you actively don't want getting in (it's commonly claimed that you should optimally give a preference to everyone, even those you actively don't want, but this is incorrect).

Usually each party would provide a list with their preferred representatives that can be modified.

Where I life, you can give up to 2 votes per representative. You don't need to choose 54 different politicians because "empty" votes will still count for the party.

Most people will just use the list of their party and maybe remove some that they don't like or vote double for someone they like.