Whether drop bars, flat, or swept-back, I believe I've figured out the two factors that must be present. First is the bar has to work for the rider (size/style/position of the bar, given the particular bike, complementing the saddle position, etc.). Second is you have to adapt to the bar based on your body/fit needs, and taking into account any trouble areas you have (e.g., pre-existing aches/pains or worse).
If you can't adapt to the bar, somewhat easily and repeatably, the bar can't work for the rider. For example, I once bought a new mountain bike and the stock bars were like 800mm wide. I couldn't adapt to them. I don't think I ever could. My road bars at the time were 380mm at the hoods.
What's more difficult is when you have a bar that could work, but it may take a long time to dial in the height, reach, tilt, grip selection, placement of controls, minor saddle position changes given how upright or tilted forward you are, etc.
I've had VO Granola bars on by Fargo for the last 8 months. They're still not perfect, but getting there. Last two rides I focused on how I contact the bars in terms of my hands/arms/shoulders. It didn't spoil the ride, dwelling on this, but I would check in frequently and ensure everything felt good and would make corrections, say if my wrist angle was awkward and would later lead to post-ride pain if unchecked (as has happened many times before). Both rides, zero pain. And they were fun, off-road rides. My hope is that I can go on a ride and barely have to check in on fit, but for now, maybe it's necessary (for me).
I think age is a factor. When I started riding serious, in my late 20's, and probably through my 30's, I don't recall ever having any fit issues. Or, perhaps, I had major fit issues but they didn't bother me...until mid 40's and up to now.