My uncle is in his mid-70s, has several health issues, but can still manage everything on his own. What I've been struggling with, especially for the last few years, is him viewing everything that's going on, including what I share with him about my life, as negative and therefore deserving of judgment/put down. Occasionally, something that I share is so hard to find negative angles to even for him, and then he simply will say nothing rather than, God forbid, say something positive. It's as if his mind is only wired to look for something bad.
Let's say I travel thousands of miles to see him where he lives. Instead of being joyous and thanking me for visiting, I'll get a ton of complaints that "but we did not get to do X" (yes, I can't spend an unlimited time visiting and do everything possible, but we did do a ton of things he wanted to do. Nope, he'll zone on what he thinks is "lacking."), that I did not visit for long enough (I visit more often than anyone I know who lives as far away as I do visits their relatives), that I needed to sleep in (jetlag is a b*tch). Let's say we go visit his cousin who has a beautiful home, is doing well, and so are his children and grandchildren. Instead of commenting on any of that after we leave, he'll zone in on "but I heard his wife had some health issue, she just doesn't like to talk about it."
I've tried talking to him about this. I've told him there's no way that everything is bad, there must be at least one good thing around him that exists. I mentioned that I too, could easily just focus on what's bad and ignore the good (much easier to do than to remain positive around someone like him, which is hard work for me), but it's something we can control. Sooner or later, he hits me with the guilt of "I'll die soon, then there will be no more [fill in a random blank he picks]." To which I'm tempted to say that we'll all die, and I might die before him, but I just stay quiet and wonder to myself why does it end up feeling that I made it worse whenever I visited/tried to have a normal conversion with him beyond small talk, and that everyone would be better off if I did not bother.
Advice? He does not believe in depression treatment/therapy, anything like that. It's exhausting to be around him, and it's a shame, because he's been like a father to me in my childhood and teens, and I'd love for us to have a more balanced relationship.
I think if you stop trying to change him and instead try to accept him, you'd have a much less cantankerous relationship. Imagine how trying it is for him, too, to be criticized for merely being himself.
You say you've noticed this especially over the last few years, and you also mention that he has a number of health issues. If those include heart disease or diabetes, just for example, then the concern is not that he's such a downer to be around but that his low mood could be a symptom of physical deterioration and must be reported to his doctor.
If that is the case then I'd lay off trying to get him to include more positivity and gratitude in his outlook, and tell him squarely that unless he wants to hurry along the road to dementia and clinical depression he needs to take his feelings seriously and share them with his medical team. Tell him you've seen the gradual change in him and you're worried about it.
But, some people just are curmudgeonly old so-and-sos. In that case you have to decide how much of him you can take and adjust accordingly.