Unlike Souter (whom many of us opposed), Gorsuch has a long record, and it’s excellent.
Gorsuch has a short record on the bench, and its been mixed. He's done some things I like (stood up for religious freedom & against euthanasia) , and plenty of things that give me pause (immigration, abortion, gay rights, etc.) Many of his left-leaning rulings are precisely why leftist slime like the New York Times and Obama's "ethics" czar are praising the pick and urging Senate Dems to confirm him, hoping he will be a stealth leftist (see Why Liberals Should Back Judge Gorsuch by The New York Times ) Like many "stealth nominees", he hasn't handed down any earth shattering decisions on any major precedents. Roberts a similar "unknown" quality, but whose background was far more conservative than Gorsuch.
The evidences suggests if Gorsuch is confirmed, he will vote similarly to Sandra Day O'Connor. For a judge replacing Scalia, that's a HUGE downgrade and would significantly move the court to the left.
Don't say you weren't warned.
History revisionism. Not a single GOP Senator opposed Souter's nomination, and only ONE major conservative organization did (The Conservative Caucus). Just like the Gorsuch nomination, they rallied behind the nomination the instant it was made, blinded trusted the President, and believed that since the judge "judicial philosophy" was marketed as a "strict constructionist", that would ensure he'd vote the right way for the rest of his life.