I disagree, I've had the opposite experiences, and in many cases the appropriate filter can cut out a lot of haze (outside), improve saturation, and when I say filters, I mean a well made filter by a reputable manufacturer. If you've chosen the appropriate filter it w/good glass, it should not be the reason for the introduction of artifacts, and I noticed you said......
"Over the decades, I noticed that sometimes led to artifacts in the pictures and some softening of the image under certain conditions."
There is always a "but" under "certain condition", which crops up. Things happen, things come up. I would be concerned in terms of your logic if it were the case that a filter would produce noticeable artifacts on a regular basis and if the filter was the cause of those artifacts.
Any piece of gear I have, including my cameras, filters, lenses will sometimes come up against a situation where artifacts are sometimes produced/a softer image than I was trying for; that's different than a lens/filter/camera generating some kind of problem on a regular basis.
I've been in Photography for 61 yrs./started using Photoshop 3 in '97 and I've haven't experienced "some softening" because I used filters in front of my optics on a regular basis and I believe that premise is too much of a generalization when you filters as opposed to which specific filter in what specific situation, and while I've had problems w/specific filters on occasion, for some "reason or other" that isn't enough of a reason for me to quit my practice regarding filters.
If you've got enough of a problem w/a filter, a problem that appears/crops up almost every time you use the filter, then I would be concerned w/using that filter, if it's a problem that isn't always a problem then it may be a problem that comes up regardless of whether you did or didn't have a filter in front of the optic, and/or caused by something else.
In one incident, I've had a filter destroyed in front of a 10 grand optic which saved the optic, and if I didn't have the filter on, a fortune goes up in smoke.
I don't care what/how most pros do it, because they don't pay for my equipment, and I don't believe my use of filtration in front of my optics is, or would be a problem causing the degradation of my images. Having said that, there are situations that come up where a particular lens/camera/lens w/a filter in front of it, will not be able to handle that particlar situation.
The filters I've used, the way I've used them have worked for me and I've never looked back.
Yes, there are arguments "for" and "against" any discussion of any subject matter, any particular way of doing something, which is what you do, and how you do it.
I appreciate by all means what you've said, and I've followed quite a bit of your discourse/dialogue in this forum, but I disagree because doing it the opposite way works 4 me.
I have a lot of respect for you when you open your mouth, believe me, but telling me it doesn't work for you, doesn't mean it doesn't work for me, and it does.
In terms of image quality, and or "artifacts", or unwanted softness, or what some pros, or what advanced amateurs do, I guess it then becomes a matter of "don't tell me, show me" to take this out of the subjective aspect into the realm of the actual imagery that you've used your gear to validate what you produce and in my case, my work along w/the filters I keep on the front of my optics.
I've uploaded a cross section of some of what I've done in my "about" section, it's here.....
I used filters in front of all my optics, and like you, I've never looked back