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.

Apple does two things that are very expensive:

1. They use a huge physical area of silicon for their high performance chips. The "Pro" line of M chips have a die size of around 280 square mm, the "Max" line is about 500 square mm, and the "Ultra" line is possibly more than 1000 square mm. This is incredibly expensive to manufacture and package.
2. They pay top dollar to get the exclusive rights to TSMC's new nodes. They lock up the first year or so of TSMC's manufacturing capacity at any given node, at which point there is enough capacity to accommodate other designs from other TSMC clients (AMD, NVIDIA, Qualcomm, etc.). That means you can just go out and buy an Apple device made from TSMC's latest node before AMD or Qualcomm have even announced the lines that will be using those nodes.

Those are business decisions that others simply can't afford to follow.