Newer nodes are hellishly expensive to develop, ballooning in cost over previous nodes. Global Foundries and most others are not working on more advanced nodes than 14nm, leaving just TSMC & Samsung with 7nm fabs. Intel has 10nm kinda crappily working, turning out low end chips that are mostly dead silicon (due to process issues).

We're definitely hitting a silicon bottleneck, the physical barriers are very real, and exceedingly costly to attempt to work around. AMD's strategy of using 14nm chiplets for components that don't scale down well (eg: analog interfaces, DRAM, etc) is likely to become much more common.