Lets hypothetically say that my meaning in life is to work hard until I die naturally. Why would I want to accept that meaning? Why should I accept that meaning?
I wouldn't accept that meaning. If that's the meaning it sucks imo.
You'll hear that life has the meaning you give it, or that you have to make your own meaning, and while it's often presented in an annoying way, there's truth to it.
As far as work, which you know I actively resent, there are different ways to interpret it.
Someone like my dad gets a lot of his meaning in life from his work, but that's partially because he enjoys the work he does and probably a good bit because it is satisfying to see the success he has had over time. It's hard to explain without giving the specifics of what he does, but it involves individual projects that test problem solving skills and end with a product he can lay eyes on and see the value of at the end, and it requires a high level of intellect - he's one of the only people who can do it. So, he wouldn't say "the meaning of life is to work hard until I die," his definition would be something like "developing a skill and pushing it to the limit, becoming the best at something and enjoying it along the way." He would never think philosophically like this, it's just not the kind of person he is, but that's my estimate.
Speaking of not thinking about it, a lot of people fall into the category you are probably most resentful of and directing this post towards. They accept the meaning they are told and move through an unfulfilling life trying to outbalance pain with pleasure and never tackling the deeper issues.
Some people actually do think about it and are happy to accept that the meaning of life is in working hard until they die. Again, their wording would be more favorable, something like "giving it my all" or "proving to myself that I can do it." Those are things that, like you, I cannot accept, but it does work for some people.
I've been putting a ton of thought into my own meaning. I don't have an exact answer for you, but I know some components. I want to learn, experience, satiate my curiosity, come to understand this nonsensical human experience, and enjoy as much as I can along the way. You could say that right now my meaning to life is wrestling with the question of what is the meaning of life. Additionally, when I hear my wife breathing gently at night next to me, I know it's not a bad answer to say I find meaning in making her life as good as possible.
To me, work is an obstacle in the way of my life's actual meaning. It's speed bumps on my road, or maybe dense traffic. Work is weight I need to carry on my journey. Work is gravity I need to overcome to fly.