Why the downvotes: because you're clearly the asshole. Or isn't this /amitheasshole?
Yes, older people have views from the past. That's because they are older people. Yes, older people bitch and whine. That's because friends and spouses are dead by now, they feel alone and forgotten. Yes, older people are not always nice. That's because things you don't even think about, like putting on clean socks or taking a shit by yourself have become hard, for some even impossible to do on their own and/or without pain leaving them with a feeling of loss and even regret for living that long.
On top of that they're literally waiting to die. And let's not forget dementia.
Now, maybe your granny is younger like 60 something, but still..
Your response to the situation lacks a lot of empathy and respect. Without this person you wouldn't be sitting there, scrolling through anime titties you clearly like just not always.
And lastly: you will be her in 40-60 years. (i don't know how old you are) You will be alone, your body will falter, your (grand) children will be uninterested in you. Etc.