During that era for the most part Intel's i7 prosumer CPUs started with 4 cores with the Bloomfield Nehalem chips in 2008 (which at the time were awesome and a game changer) and ended with 4 cores with the Kaby Lake-S in 2017. It really only changed in 2017 with AMD Ryzen forcing Intel to actually increase core count.
2008 Nehalem benchmark: https://cpu.userbenchmark.com/SpeedTest/778/IntelR-CoreTM-i7...
2017 Kaby Lake-S benchmark: https://cpu.userbenchmark.com/Intel-Core-i7-7700/Rating/3887
When I compare the two, it shows an effective 20% speed increase, although microbenchmarks show a 50% increase. That is a stagnation.
During that era it felt like a lost decade. I don't miss it.