>>64148204
Big shakeups in firearms design came from breakthroughs that were inarguably superior- centerfire primers, and smokeless powder both spurred on innovation. Then industrial advancement in the 1900s-1940s gave us things like stamped guns and WW2 really pushed firearms design and production at insane scale. After WW2, that same stuff was tinkered with alongside intermediate cartridges.
We had all the major stuff figured out by the 60s. Innovation after that has either been incremental or innovation for innovation's sake.
The biggest gun shakeup since the 60s has probably been Glock popularizing simple striker pistols.
Otherwise trying to start from scratch is competing against a mountain of refined design. Until something so inarguably better comes along that makes current firearms tech look like a flintlock musket compared to a centerfire bolt action, we won't see jumps in guns.