I'm mad about Trump abusing his power and appointing 3 justices
The thing is, there's nothing in the Constitution limiting how many Supreme Court justices a single president may confirm. For instance, a total of 11 were chosen by George Washington. If there's a vacancy then the President is allowed to nominate a new justice. If a majority of the Senate goes along with it, then that justice rises to the Court.
It's true that Trump appointed an abnormally high number of justices by recent standards. Reagan was the last to have more than 2, and he had two terms. But that's a matter of coincidence. There's only 9 people on the court, and average life expectancy for Americans is in the mid-70s (your average rich and well-educated person will enjoy a longer life still). So normally there's not that many instances where one dies or retires. But Trump got lucky.
Think what you want about the Senate refusing to confirm Merrick Garland (Obama's pick to replace the right-leaning Scalia) and waiting until Trump became President to let him pick someone else. It was within their legal purview to do so, and I have little doubt that Trump's picks would've been blocked by Dems had they enjoyed a Senate majority during his term.