

I sort of agree, weirdly. Funerals are weird, OP, as is family. As someone with a horrendous family and a very bad social brain, I totally empathise with saying you have ‘no bandwidth’. But you only get one father, and one funeral for him. This need not be a long and drawn out event.
In your position, I’d tell him you’ll go and you’ll have a shitty time and you’ll really hate it and let him know you’re doing it for his sake. That way you’re not lying, you’re just agreeing, in the worst case, to waste a few hours of your life with some unpleasant people.
Even better, tell him you want a nice time out now, like a nice dinner, as payment for enduring his funeral when the time comes.

This is a legimately awful response.
OP has already said religion isn’t the issue and that a dramatic, judgmental family is.
Calling OP whiney and immature is baseless and unhelpful. As is telling people they should just suck up doing uncomfortable things ‘because it’s the respectful thing to do’. Being an adult is realising that there is actually no ruddy obligation to go do a lot of these things out of respect, especially when, as in OP’s case, you’ve clearly run out of respect for the people in question.
Yes, there are times when we must all do uncomfortable things - When those things come up, work out why said thing is actually necessary or beneficial to your life (or those you care about), and then you, as an adult, can actually weigh up those reasons and work out if you should ‘suck it up’ or not. It is very much your own choice, not some god-fearing obligation to respectfulness.