Death is really terrible and it carries massive guilt.
I am 2 years on and I think during this lockdown is the time it's really hitting. I have stayed so busy for 2 years, basically running from dealing with it, just to keep going.
It had obviously hit me during the nights for the last 2 years but now I find myself in the day running through every interaction of every second in the last few months, weeks, days and hours on the run up to my mum dying.
She was my best friend, an amazing mum and proudest Nana in the short 6 months she had. But I am told guilt is a massive part of any grief, I am going back to feeling guilty about stuff when I was 14, younger and things between her and my father that I should have protected her more. Which I know is ridiculous, it wasn't that bad and she wouldn't have accepted it and I was there for her and ultimately made a stand that made her leave.
I went through the PALS to query and ensure I was comfortable with how they handled it, and I still hold her GP slightly responsible for not acting quicker and I regret not actioning that concern through the proper channels.
Ultimately though, yes you are right, in most cases it's no ones fault and people normally act in good will with good intention at the time, so you can't change things, just know you did your absolutely best.
Sorry to ramble p, But I do understand the guilt feeling, but be kind to yourself, you did your best.