It can be seen as also the miners' fault. Core does not have all the power to change everything. They have a proposal, it is Segwit. It is clear that the support behind it is not enough, then why blame everything to them? The miners are also at fault here. I have a feeling they want everything to stay as is so that they enjoy more profit if the fees remain high.
It could also be them who is spamming the network. Spend a little in fees to get a little profit in fees.
Imagine two mechanics own an autobody shop and there's a car that needs an oil change.
One guy wants to do it the simple way: drain the old oil, and pour in the new oil.
The other mechanic says "no no, we can't do it that way, we might spill some oil,
so we're going to do a fancy engineering project that will cost 5000x as much.
It will involve dissassembling the car, building a separate garage, its going to
take 2 years, but that's my plan." If the mechanics disagree, who's fault is it?
Raising the blocksize is the obvious simple move (literally 1 line of code), and it was the Satoshi's plan from the beginning.
Miners all favored it, but it was Core who blocked that with their influence, and then came out with segwit which is
literally 5000 times more complex (5000 lines of code).
You decide who is at fault.