Is this the fate all people are doomed to as they age?

Dad is 66, formerly a practical man who once focused on getting the best out of any situation and refusing to be beat by negativity.

He’s been retired almost two years and now his small talk is based on a things that annoy him. When idle he watches British and American politics - I suppose they are rants rather than news reports - and has generally a dim view of everything.

I try to get him out the house regularly and give him lots of time with his granddaughters to keep his mind active. But in the short space of two years he’s gone from pragmatic capable guy to a grumbling old git.

Do I keep trying to give him other things to think about other than online rage or let him become just another angry old ranter?