Don, couldn't an analogy to your question of whether restorations aren't drastically impactful because "the land, site, routing is unchanged," be asking a homeowner who'd just spent a year remodeling if they thought the finished result wasn't any different because the square footage remained the same? I don't think that homeowner would be too pleased to hear a question like that.
I'd like to think that architecture, the quality of the greens, and the routing are still the most important factors for top 100, especially Golf Magazine's, but clubs can (rightfully) lose their rankings on account of not being considerate custodians of their property and their original architect's work. What these restorations have done, especially at Oakland Hills, Baltusrol, Inverness, and Oak Hill, showcase just how sound their course's earliest iterations were, and in hindsight demonstrates just how much clubs can miss the mark by not taking proper care of them.