Queen I am REALLY not talking about parents like you
Might help to be clearer in your OP.
"Simply saying you are doing your best for your children is not a get out clause. Sometimes your best is not good enough."
Sounds generic and is judgemental to me. I am quite sure that you are doing your best too OP as most of us are (who doesn't do their best?). To many others doing our best may seem to fall below standard.
We all have different priorities. For some being super duper organised and never missing a school event is the most important thing. Other parents prioritise healthy food and great homework support. Others still spend a lot of money and energy in supporting dc's talents & hobbies.
We can agree that none of us are perfect parents and that we all lack in a several areas but we all do our best as we think is right by us and our children.
However it seems that you are specifically talking about a family who is seriously struggling and not really to "hate the phrase - I am doing my best?" in a generic sense.
It's true though, some people are poor parents on the whole mostly because they themselves have not been parented well, have mental health issues or find themselves in bad relationships and deprived socio economic conditions. I feel very sorry for people like this and would try and help where I can. I have previously volunteered for a charity supporting young families and I can assure you that they need support not judging.
Do you really think you will never ever fall on hard times OP and let more thing slip than you'd hoe? Or are you a parent who hasn't got any shortcomings whatsoever? With those short comings, you are probably still 'doing your best'.