There's always some excuse.
In this situation, I would say that anyone who is high risk and has no affirmative reason to believe Vitamin D is contra indicated should consider trying to take a small supplement and/or get some sunlight regularly.
For optimal absorption, you need to take Vitamin D, Vitamin K and Calcium together. Some Calcium supplements include those two vitamins.
For optimal results, do not consume calcium and iron together. This means if you are trying to improve your nutritional status via diet, do not eat high iron foods (like beef, broccoli) with high calcium foods (like cheese, milk). They interfere with each other in terms of absorption.
If you are in a really fragile state of health, all these details and more (such as bioavailability) matter a helluva lot. If you are not in a really fragile state of health, you may find that you don't need to care so much all these pesky details.
Anyone who is really interested in their own welfare can and should start a food and symptom journal and read, read, read about health stuff (and learn how to sort the wheat from the chaff). If you do that, you can get to a point of noticing symptoms of deficiency at an early stage.
I do this regularly and adjust my diet accordingly.
But these are not answers people want to hear. They want a pill, a shot, a surgery, a solution with a really big and obvious and immediate change so they can look at it and go "I did a thing and got a result." They don't want to hear "You need to track it over time and see how you feel in a week or a month to have any real idea what helps."
It's also inherently hard to isolate nutritional stuff. If you make any change at all to your diet, you have probably made multiple different changes.
The way to isolate it is to start with supplements, stick to your normal diet, make no more than one change per week and keep a journal so you can track it and see what happens.
Anything that has any health benefit will have side effects. Antibiotics routinely cause diarrhea and that's one of the more common side effects of alternative remedies, yet if I tell people that many of them will use that as an excuse to say "Oh, it has side effects. Nope. That's a big fat nope for me. I'm not doing that." even though it's the same side effect that antibiotics have and they wouldn't hesitate to take those.
There's a lot of ignorance and prejudice and inherent resistance to resolving medical things nutritionally. In spite of study after study after study saying "Nutrition and exercise mitigate every known deadly medical condition ever in the history of human kind" when the rubber hits the road, people hand wave off nutrition as not important and "not something that will cure cancer, you dumbass!" and stuff like that.