Agreed. Having both around is a nightmare, I still can't believe they ever did it this way.
The other place MS has not executed well is versioning/naming and the communication of those versions/names. But soon(?) it'll all be .NET Core and we can put this behind us.
I don't know if there's a good way to migrate the csprojs automatically (maybe https://github.com/hvanbakel/CsprojToVs2017?), but it shouldn't be that hard manually (by creating a new project), assuming you have just a few projects to migrate.