I have to agree with this. Myself, and a number of neighbours, and quite a number of people I've known over the last 25 years or so have reported different things, (animals in distress, animals left alone, animals struggling, animals suffering,) all to the R. S. P. C. A - and they've done absolutely nothing about any of them.
As you said, unless the camera is on them - rescuing a kitten out of a drain or something - they don't do anything, and they don't want to know. I don't see the point of them, really. All they want to do is prosecute people, and shame people. Some people deserve it, but some do not.
I remember a neighbour of mine some years ago. She was in her early 60s and she was disabled - poor mobility - and she was struggling after her young adult son had got a guinea pig and had left home suddenly, and left the guinea pig with her.
It was difficult to look after (for her) and ended up getting a little bit messy - and his cage was not being cleaned properly. Someone reported it to the RSPCA and instead of trying to help and advise her, or saying 'look, this guinea pig is not being cared for properly. You clearly can't cope,' and taking it off her to give to someone else to look after, they went in all guns blazing, treated her like a monster, and decided to prosecute her.
She had to go to court, had a £1000 fine given to her, (which she had to agree to pay in instalments of £30 a month as she had very little money,) and she had a criminal record for animal neglect. It absolutely devastated her.
The story was in the newspapers and she was labelled being 'cruel to animals.' The papers embellished the story, and made her out to be an evil cow who had been plain cruel to this guinea pig, when all it was is that she was struggling to cope with him.. All that should have happened is he should have been taken off her. That's it.
She actually died about a year after the prosecution - and only in her early 60s. I'm pretty sure that the stress of this contributed towards it.
That happening, along with the fact they don't seem to give a shit 90% of the time when someone reports an animal in distress, has made me loathe and detest and despise the RSPCA with all my heart. They only turn up when there are glory points - or a prosecution in the pipeline.