Trump took his list directly from the Federalist Society, abdicating his own responsibility. This was done to get their support for POTUS. He wasn't a bastion "casting the net wide". POTUS pick their nominees for a variety of reasons, nearly all political since the 80's at least.
Trump didn't be cast his net wide, but this isn't a fair characterization of how judicial nominees have been picked since the 1980s. The Fed Society has definitely had influence since Reagan. That is true, but if we're talking about ideological diversity, Republicans have been wildly more diverse than Democrats have been.
Prior to Trump, Republicans appointed conservatives (Scalia, Thomas, Alito, and Rehnquist), moderates (O'Connor and Kennedy), a right-leaning moderate (Roberts), and a liberal (Souter, also Stevens if we go back to Ford).
Democrats haven't appointed a conservative since before the New Deal. All of FDR's appointments were partisan Democrats from a purely political angle, and they would all rubber stamp his particular agenda, but there were was some diversity beyond that. None were conservative, but Hugo Black and William O. Douglas were not similar.
JFK appointed a moderate in Byron White. Every Democratic nominee since has been a very solid liberal. They aren't all identical, but they're close. There's a hell of a lot more room between Anthony Kennedy (and especially David Souter) and Clarence Thomas than there is between Stephen Breyer and Sonia Sotomayor.
The point is that if we're judging how wide the net is, Democrats may not have a public organization comparable to the Fed Society, but they have a process in place to pick nominees that is keeping the net at least as narrow. Their record of ideological consistency and uniformity is much stronger at least for the last 50 years.
Another thing, we really don't know what Trump's nominees will be like - not for sure. I suspect that Gorsuch will be a pretty reliable conservative (though he voted with the liberals on reading transgenderism into the Civil Rights Act - can't imagine any liberal justice departing that far from the orthodoxy). Barrett likely will too with a few hiccups along the way. Kavanaugh? As much **** as he took when he was nominated, his record wasn't that of a militant conservative. It frankly looked slightly to the right of his predecessor - about like Roberts.
So your point isn't totally wrong, but like I say to Switzer, remove the plank. Let's see a Democrat appoint someone who isn't a solid liberal (like Republicans have appointed many who aren't solid conservatives, and then they'll have the right to complain about the Fed Society.