Their failure, or inability, to release tick/tock updates on Intel, was surely biting them in the ass. How much revenue was lost by not updating the trash-can Mac Pro for six years?
Also, trashcan Mac was Apple's own self-inflicted damage, and nothing to do with Intel.
A lot of the issues with lagging updates to anything that's not iPhones are also precisely because there's no time and non resources to focus on anything but the next release.
My assumption is that the devices that aren't being updated regularly aren't big sellers. If they were then they would get more attention.