Decode overhead is fairly fixed, and proportionately has become tiny over the decades. Most larger instructions dispatch to microcode, and compilers know better than to use them much.

There's a price to x86, but for larger cores it's pretty small, we've learned to work around it.

Apple bothered to do the things Intel was too lazy to do for so long, particularly improve the ooo and other resources to where Intel didn't want to spend the silicon. Intel has always been cheap, nickel and diming their way out of performance, this is the cost.