Their tech really didn't push boundaries that much, at least not usefully, in recent years.
The distinction to make is that it was poorly applied. That doesn't mean it wasn't there. id tech 4 and 5 were examples of id taking Carmack's latest idea and running with it full stop, even if the tech wasn't ready.
Other developers eschewed these technologies in favor of older ones, because they had the focus to pick tech they could apply immediately and successfully to fulfill their vision. id didn't have this focus, and the games clearly suffered as they made the games to suit the technology. The so-called "tech-demo" syndrome that everybody uses to describe the latest id games.
Eventually those technologies made it into other games. Per-pixel shading is all over the place now, but still alongside lightmaps. Megatexturing is so compelling that support for it is built into the latest graphics standards, so that games can use it properly and without putting in the monumental effort that Carmack did.
You can't say that he wasn't pushing boundaries. Come on. It's all right there. The games were failures, and other engines look better in many aspects, but the tech was there and it was ahead of its time.