So, I will say this... I unfairly credited Mackie for X-Men Unlimited 4 which is just so, so bad - but it turns out that one was Lobdell. Mackie did write a couple of other issues of Unlimited, as well as Chromicles.... he was responsible for my least favorite X-factor run when Mystique, Sabretooth. and Wild Child had joined. And remember when he added Fixx, Archer and Greystone? Good times... He wrote X-Factor for its terrible final 30 issues, and sure he had the misfortune of following Peter David, but dear god...
And then he turned that title into Mutant X and barf.
He wrote the various Gambit and Rogue minis which were just such boring nothing burgers...
He's clearly not as bad as Austen, and maybe he's not even as bad as Ben Raab or Marc Guggenheim (apparently, I didnt read X-Men Gold)... but he's part of that era when so much of the X-Men got so terrible.