Absolutely no one has said that. Starfleet’s decision to not help the Romulans is on Starfleet and Starfleet (And the Federation) will have to own up to that. But this series isn’t about Starfleet, it’s about Picard. And Picard gave up. It’s just that simple. That’s the point you seem to be missing here. He not only walked away from Starfleet, he walked away from Raffi, he walked away from Elnor, he walked away from the Romulans. And his walking away...hurt people. His walking away had consequences. And he is responsible for that.
You keep saying everyone knew the situation and quite frankly, you don’t know that. We haven’t been shown that on screen. I think it’s a safe bet that the Klingons wouldn’t have been willing to help the Romulans, but OTOH, Jean-Luc Picard is no ordinary man in the eyes of the Empire. He was K’mpec’s Aribiter of Succession. He was the former commanding officer of the Ambassador to the Klingon High Council. Picard’s voice held weight within the Empire. Did he go to Worf or Martok and at least try. The day Starfleet accepted his resignation did he go straight to the Federation President? Did he go to the Federation News Service and do an interview? No. Knowing that Raffi got discharged because of him, did he ever check up on her? Did he go to the CnC and advocate for her? Did he return to Vashti to explain what had happened? Did he ever check up on Elnor? Again no he did not. This is not about Picard failing to persuade the Federation to rescue the Romulans. This is not about him failing to rescue the Romulans. This is all about him no longer trying, about giving up, about Picard waking away from the people who cared about him and those who needed him. You say he didn’t have any responsibility for those people...of course he did.
Resigning from Starfleet was the right thing. As a military officer there is a point beyond which you cannot take the argument. The answer was no. That's it. Even if he didnt threaten to resign, it was the right thing to do. He tried, he staked his career on this, and they are just not going to do it. Either accept that decision and continue on with your career in uniform, or quit. Quitting was right.
This was a policy decision the President and Federation Council would have made, not just Admirals. The military doesnt rule the Federation. This was known to everyone already. Planets are threatening are threatening to secede, this is a major issue of public policy. He feels bad, and thinks he should have maintained some of the personal relationships he had with others. I never had any problem with him feeling bad about it. I get that. We all do.