Arguing a case in front of SCOTUS still means something today?

It still is but current SCOTUS of US has lost a lot of credibility in essentially making Presidents 4 to 8 year kings who can't be sued or charged with a crime. There are other things like the newer judges lying while under oath that they weren't joining up to end decisions on civil rights and ending abortion as a basic right.

As a layman, I thought that was a bit of a prestige deal. Is it not?

Some would say it has lately become a bit of a kangaroo court.

Put enough money into the right-wing hands and anything is possible