The "SDK project model" did a lot to reduce that back down. They did break the BCL up into a lot of smaller packages to make .NET 4.x maintenance/compatibility easier, and if you are still supporting .NET 4.x (and/or .NET Standard), for whatever reason, your dependency list (esp. transitive dependencies) is huge, but if you are targeting .NET 5+ only that list shrinks back down and the BCL doesn't show up in your dependency lists again.

Even some of the Microsoft.* namespaces have properly moved into the BCL SDKs and no longer show up in dependency lists, even though Microsoft.* namespaces originally meant non-BCL first-party.