Not to be blunt, but doesn’t this necessarily mean you didn’t let go? But how does one “just let go”? Your mind may not feel there’s a justification or reality behind letting go, so it failed, but I’d say it’s based completely in honest seeing, and it comes from insight. It makes sense to let go, but don’t take my or anyone’s word for it, how could letting go make sense? What is the actual insight for this situation that would help?
I’ve been in your place before and it felt inescapable, but after I relatively calmed down, I could reflect on this carefully.
One main way to react when one sees the suffering of others would be the brahmavihāras. You could check out Venerable Upekkhā’s guided meditations for this in serious depth.
When you see others’ suffering, you can respond to this by giving loving-kindness and compassion to them; wishing for their happiness. It looks like you already have this honest intent.
You can respond with appreciation - look at what the world does have, which is actually a lot. We’ve ended a lot of world hunger, we’ve fought for a lot of rights, and we even take things like having communication, this website, functional legs, fingers, digestion, this breath, and every atom of oxygen which fuels this body for granted.
Then there’s equanimity - indifference (not laziness or by not taking action, which you should if given the chance, but by perception) - being content even with these injustices.
I would see that there’s no real reason to suffer over others’ suffering, even if it is a lot, even if it’s completely unfair, even if it did come from those beings’ choices (as @Notez’s sutta is talking about), even if it’s my family’s, or even if it’s my own. I can recognize such suffering and problems for its depth and complexity, and even derive sadness from it, but the good news is that there’s still no real reason for suffering, and everything does point to letting go and happiness being truth.
My suffering is part of all the suffering, so if the “goal” is to remove the world’s suffering, wouldn’t adding more suffering be ironic, and create more of the same problem? Other beings have their problems, it shouldn’t be made about “me”. Suffering over it isn’t going to solve anything or do anything for them, it goes the other way. Being hindered, suffering, fettered down, especially restlessness, annoyance, or rage would make helping the world more difficult. It’s harder to function with those things, so it’d be harder to solve those problems. It’d even be compassionate and virtuous to develop myself away from those things, as it would improve and change my interactions with others (including animals) to be peaceful and rational. Meditation is therefore not just about myself.
There really is a lot of suffering, it’s indescribable and it’s very real, don’t look away or push it away, look right at it. In fact, just seeing how much suffering there is can even be a source of confidence, to practice deeper and with conviction - check out SN12.23 “the vital condition for saddha is dukkha”.
So ignorance is a vital condition for choices. Choices are a vital condition for consciousness. Consciousness is a vital condition for name and form. Name and form are vital conditions for the six sense fields. The six sense fields are vital conditions for contact. Contact is a vital condition for feeling. Feeling is a vital condition for craving. Craving is a vital condition for grasping. Grasping is a vital condition for continued existence. Continued existence is a vital condition for rebirth. Rebirth is a vital condition for suffering.
Suffering is a vital condition for faith. Faith is a vital condition for joy. Joy is a vital condition for rapture. Rapture is a vital condition for tranquility. Tranquility is a vital condition for bliss. Bliss is a vital condition for immersion. Immersion is a vital condition for truly knowing and seeing. Truly knowing and seeing is a vital condition for disillusionment. Disillusionment is a vital condition for dispassion. Dispassion is a vital condition for freedom. Freedom is a vital condition for the knowledge of ending.