There's no probably about it or thinking required. That is literally the law. The President nominates a replacement, and the Senate votes to confirm it or not. There are plenty of layers of politics, posturing, and pomp added on, but the law is simple and clear.

But it hasn't been followed in some time. The last president did nominate a replacement, and the Senate elected not to vote at all.

I mean legally it's always been this the Supreme Court has been very clear on every cases regarding confirmation that Congress is free to act or not act at it's leisure.

This wasn't always the case, here's an excerpt from the wiki on recent changes making this the case: "Senate cloture rules historically required a two-thirds affirmative vote to advance nominations to a vote; this was changed to a three-fifths supermajority in 1975. In November 2013, the then-Democratic Senate majority eliminated the filibuster for executive branch nominees and judicial nominees except for Supreme Court nominees by invoking the so-called nuclear option. In April 2017, the Republican Senate majority applied the nuclear option to Supreme Court nominations as well,[2] enabling the nominations of Trump nominees Neil Gorsuch and Brett Kavanaugh to proceed to a vote.[3][4] "

That’s just the Senate deciding internally what its procedures are. Either way, the Senate is making the choice.

The filibuster has always seemed anti-democratic - it’s not in the constitution, and I’m pretty sure that historically it was a way to make give the minority senators more power at the expense of the people.

The people are represented by the House of Representatives. The Senate represents the land.

Interesting, so if Trump can nominate and pass another judge, it'll be by using the rule that the Democrats changed in 2013 to benefit themselves.

To be fair, they passed the ruling for non-supreme court justices. Republicans extended it to include them in 2017. Still, an example of terrible governance and foresight on both sides.

That would be incorrect, unless you are talking about a regular federal judge and not a Supreme Court justice. In the latter case, it was a rule the Republicans changed in 2017 to benefit themselves.