There is nothing Democrats could have done to stop it. Republicans have a majority, and they gambled for that seat and won. The reason those Democratic Senators voted for him was to curry favor in Trump states, as they all knew Gorsuch was getting confirmed no matter what. There was no point in casting a vote that could possibly hurt them in 2018.
Symbolic opposition isn't always the best strategy for every Democrat.
This deluded thinking is why Democrats are as unpopular as they are.
This is... just empty concern trolling. Like, if you really think that those three senators voting against Gorsuch would have changed anything, you're either completely disingenuous or literally mathematically illiterate.