Innovative games are hard to make, especially sandbox games. For example gtav and skyrim sold like hotcakes, but it takes many many years to create an open world game like that. Most companies will just stick with existing ideas and repackage them, to keep profits high and costs low.
Also ea and activision have made their name buying existing franchises, milking them dry, then throwing them away as a cheap buck. Ea killed ultima series, and I forget which one bought the rights to wasteland, but it was the spiritual predecessor to fallout. The company refused a wasteland 2, the developers ended up making the game elsewhere, under the name fallout.
Then there is cost of groundbreaking games to profits. Many groundbreaking games never sell at first, and takes years of word by mouth to get a fanbase going, while reskinning a cod game has a guaranteed fanbase. The first elder scrolls game initially sold only 3k copies, despite being the most expansive of the series on primitive dos. Ultima underworld came out in 91 before wolf 3d, and it was a full 3d game, with jumping, swimming, looking up and down, spells, armor, need to sleep amd eat, and an interactive system requiring you to handle every faction on a way as to not make them hostile.
Wolf 3d however coming out later sold way better than ultima underworld, part of it was the fact that wolf 3d needed only a 286 while ultima underworld needed a 386, but the main reason was it was a complex and innovative game, much like elder scrolls arena, it did not catch on until long after it's time. Video game designers tend to avoid the previous examples, by sticking with what they know will sell.
