I've watched the games shown on BT and in my opinion, the standard is below L1 , possibly top of the conference, maybe a little better. Obviously that excludes Celtic.
I saw Taylor's goals on Sky and the defending was appalling.
I've watched Scottish football on and off for a number of years and I do think the standard has fallen. As others have pointed out, twenty or thirty years ago the best Scottish players often went into our top league and were still good players, Dalglish, Hanson etc but the top Scottish players now struggle to do well in the Championship. Obviously that's partly to do with the huge lift in standards we've seen in the English leagues.