I didn't mind the second part of Slash's solo on Hard Skool, but the work on the final track seemed uninspired overall. I actually liked his Absurd guitar work, but find the mix atrocious. Same with Hard Skool on the mix. I wish they would minimally have Slash and Duff on the new material (much like how they had Bumblefoot on CD) and actually write and record new stuff with NITL.
It's not too late to go this route, where they have a hybrid album (or two, depending on how many songs NITL can actually create) with CD era songs with the superior mixes of those songs from that time with properly mixed new songs or completed unfinished songs from the CD era.