Not if you live at a latitude above 37 degrees north (which is two thirds of the U.S. northern region), if you live there you're not getting enough of the hormone that comes from Vitamin-D.

https://www.health.harvard.edu/staying-healthy/time-for-more-vitamin-d

Also, if you're of African American or Hispanic American and have dark skin, you need a lot more sun exposure than Caucasians to get any Vitamin-D.

The only real way is to check your blood levels, be above or around 50 ng / ml and you will superior blood levels. I use an at home blood test called Cerascreen and check my levels maybe 3 times a year. For example if my blood test came back with a result of 47 but I want to be around 60 I would use this calculator to calculate my weight and current blood levels and it will show me exactly how many IU I need to get to 60 (which is 2100 IU a day):

https://omegaquant.com/vitamin-d-calculator/

It's also important to note that you can overdo Vitamin-D which is why you must test your blood levels before you take any supplements. Because you don't want to be taking 10,000-50,000 IU or some insane amount every day as you will over-calcify your blood and you can probably get very sick.

Another thing if you have to supplement and you live above the 37th parallel and can't get it naturally is to take K2 in combination with Vitamin D3. Vitamin-K2 is found in dark leafy green vegetables like kale and spinach and fermented foods like Kefir and Kimchi.

K2's only job is to transport calcium out of your blood and arteries and it chaperones the calcium to the body where it's needed like the bones and other places where calcium is needed. When you're supplementing Vitamin-D you are getting calcium in your blood, that is why it is super important to take them together so you get the health benefits of Vitamin-D and ensuring you are not over-calcified.

There's a really great video about K2 here:

https://communities.win/c/GreatAwakening/p/15IrUJ8BN5/incredible-interview-on-vitamin-/c

So if you're testing your Vitamin-D levels regularly, you're taking D3 daily at the right amounts according to your weight, you have no worries. As long as you're not too low or not too high and you maintain levels between 50 - 60, you're good.

I understand your concern about Vitamin-D and companies taking advantage, but if you want to stay healthy and out of the hospital for a synthetic respiratory virus like Covid, then you probably want to supplement. This study shows that people with low vitamin D levels had a greater chance of ending up in the hospital for the respiratory virus:

https://www.cureus.com/articles/76496-therapies-to-prevent-progression-of-covid-19-including-hydroxychloroquine-azithromycin-zinc-and-vitamin-d3-with-or-without-intravenous-vitamin-c-an-international-multicenter-randomized-trial