That's actually a good question. The people to blame are the people who lied to these kids and people (dudes especially) and did not keep it real when discussing life and society. This goes both ways, since female incels are also a thing, as LSA and such shows. A lot of their issues come from a lack of personal accountability and a bubble-bursting that occurs for them when they go out into the real world. They realize the world is not as they have perceived it to be and being forced to realize they are wrong is too much for them to bear so they assume the world as a whole is wrong. It would be one thing if their issues had some basis in facts like stats but the fact that it often doesn't brings them back to square one. Some of this applies to some male incels but this seems to be the bulk of female incels.
For men, we all too often will claim "men and women are equal" then at the same time advocate gender roles that put forth a level of burden on men (men are supposed to build, be stoic, and lead and if not, then you're not a man and so on). At the same time we allow women more leeway in regards to this. There is a valid reason for allowing that leeway but we shouldn't bullshyt kids and act as if the kids are full of shyt or incels for questioning all of this. That is where their resentment comes from.
I'll also add that a lot of this also stems from talking down to boys and men instead of talking to them. It doesn't help that much of the talking down to comes from people that these boys see as an enemy - they see said person as someone who hates them or looks down on them since many of these people were at one point, calling these boys "loser" or some variation of it. It also doesn't help that the mere idea of talking to them as normal human beings is seen as coddling. The weirdest shyt since the "tough love" approach has been tried for years now and it not only is not working but we're seeing things become worse.
As for the solution? Hard to say. The strength of the the "redpill" is that it is based in some truth. Some facts here and there are valid. The imbalance is real. That doesn't mean it is bad in some instances, but it is real. This is where people who often oppose incels fall apart on: they operate on this men= evil, woman =good mentality. This is why the issue will not go away in our lifetime and in fact get worse. All and any effort to fix things will be watered down and rendered ineffective by these people pushing their own agendas. We have some in this thread right now. The incel does not see their efforts as an attempt to help or fix but merely subjugate. These particular people opposed to these incels don't care because that is in fact what they want but that's another discussion for another day.
Moreover, the problem is that hating women is trendy because being an abrasive a$$hole is trendy. It doesn't help when the people talking down to these boys thinks being an abrasive a$$hole to these boys so they can stop being abrasive a$$holes will make them stop when in reality, it won't. It never does.
As mentioned before, talking to these boys as if there are normal people does wonders since being treated with a lack of human decency, perceived or real, is what creates a lot of these incels in the first place. Being honest with them about the world works too while at the same time, getting them to focus on improving themselves so they can have a greater chance to dictate their own lives within the world helps as well. One has to guide these kids to the middle slowly but surely. Going full "men = bad, women = good" is a recipe for disaster and why this problem continues to get worse with time.