I do have sympathy for those with dark(er, which is basically everyone) skin who may not be able to directly tell the efficacy.
My concern is that mineral sunscreens are difficult to apply and leave a film on the skin (which is the entire point, I guess?); i hate that feeling, so I use chemical sunscreens. I'd bet that some of them have very nasty long-term side effects. So in the end i almost always go with trying to cover my skin with clothes/shade/whatever if at all possible.
Why?
Chemical sunscreen that avoids this is designed to sink into the skin like lotion. So there's something literally in your skin blocking uv or it won't work very well. I'd say this increases the odds of circulating something carcinogenic or otherwise toxic into your bloodstream.
It's hard/impossible to find in US formulations but in AU and EU some higher end brands use it. I like the La Roche Posay Anthelios series of sunscreen - I believe they all use Bemotrizinol as the active but I am 100% sure this one does: https://www.laroche-posay.com.au/sun-protection/face-sunscre... - Note that the formulation for the specific product is different in different regions, this is the Australian version.
They could also have a lot of short exposures, like someone who is only outside for 5-10 minutes at a time but 2-3 times per hour every day, as was the case with one of my early jobs that involved walking between buildings a lot.
A common mistake to make is believing that if you're not burning, you're not accumulating damage.
Endocrine disruption: Oxybenzone (BP-3) and related benzophenone-type UV filters have demonstrated endocrine-disrupting properties in vitro and in animal studies, with some human data suggesting possible hormonal alterations and increased risk of uterine fibroids and endometriosis.[6-7] However, most human plasma concentrations are much lower than those producing effects in bioassays, and current evidence suggests low intrinsic biological activity and risk of toxicity for most organic UV filters except oxybenzone.[8-9]
Contamination: Benzene, toluene, and styrene have been found in a large proportion of sunscreen products, likely due to manufacturing processes rather than the UV filters themselves. Benzene contamination is a particular concern due to its established carcinogenicity.[1]