My whole extended family is like 10-15yrs apart from their spouses, so I am pretty confident that is can be perfectly well and fine. I see it mostly akin to dating someone from another country. Will there be a higher likelihood of difficulty understanding/relating naturally? Yes. Does something have to feel natural in every respect to be good? No, learning to truly care for another is often not intuitive and a feeling of super compatibility has led many into bad marriages. Is there a higher risk of one person getting exploited? Depends. That seems to do with various metrics of power that often correlate with age but have no real connection to it. Are there millions and millions of examples of it working out fine? Yes. Yet is there a higher chance that one of the parties will decide that it isn't actually what they want? Yes. However that is no moral issue if both are perfectly aware of that obvious chance and are simply finding out if it can work. That is what we all do with someone new.
So long as everyone involved is adult and in control of their own life (so as not to be manipulated), there shouldn't be outside moralizing. When you're talking younger ages like 19-20, is there age-specific likelihood of changing their mind later? Yes. However, while realizing what one really wants and the time invested into not-that might involve some regret, that doesn't necessarily mean it was a mistake or lacking wisdom. Lacking wisdom also shouldn't stop one from living life, since we all generally lack wisdom in things until we become more experienced. One should have a mind for safety and there are some situations that can exist in age-gap relationships that have risk, but there are plenty of risk factors in existence that have nothing to do with age disparity as well.
I think parents who are overly concerned/controlling about their adult children need to learn the important transition taking place, which has already been happening over time. Everyone needs the freedom to live their own life and experience their own successes and failures. Acting as a dominant hand over a grown child, requiring them to have and practice your personal sense of wisdom in order to not aggressively counter their wishes is abusive. Policing their sexuality is creepy and abusive. Yes, when they are actual children it is proper to protect. When they are adults you may still not wish to see them ever experience hurt in this life, yet they are adults and they choose for themselves. It has to happen at some point and that point should be related to their capacity to understand and bear consequences, not their capacity to agree with you about what consequences are likely to be or if they should find willingness in themselves to bear the risk of them.
It does get a little muddy if the consequences end up falling on the parent, but as I said, if everyone involved is grown and in control of their own life, outside pressures should keep out of their business. It is the case even in plenty of people in their 30s that they are not really in control of their own life and can be victimized more easily and the consequences fall on others around them as well. In such cases, I am more sympathetic to people who wish to voice their opinions into the situation. However, these sort of things, often correlating with age, are not actually determined by age. Lots of people find themselves in a 3rd unhealthy marriage after 30 years of grown adult love life.
As for my personal experience, I have never deviated too far from my age. There was once when a woman in her early 20s was quite a bit more mature in certain ways and family-minded than most women substantially older, yet she was so family-minded that she allowed her life to be subservient to her family instead of seeking what she wanted. As a friend I couldn't support her in choosing against herself, so I certainly wouldn't ever do so as a romantic partner, especially if her choice against family was myself, so I never pursued anything even though she showed many signs of loving me. That is the closest I have gotten, as most younger ones are so indoctrinated with whatever their particular indoctrination is that it feels impossible to relate to them. I need someone who is their own and choosing freely, not letting their notions of expectations upon them decide. That is much more common in those closer to my age, yet still rare.
Still, I can see the appeal aside from the obvious sexual sides. Less baggage, more playfulness, more readiness to give love a try, more openmindedness. Bad experiences turn people bitter and turns dating into more of a job interview than sharing things together. Men are constantly sized up by everyone all the time, they aren't looking for that from a romantic partner. They want a companion, supportive and caring, connecting to what makes life beautiful, not what it requires to function. They don't need to fix anything, they just need to not become another voice of performance evaluation lost in the millions of others. It's similar to how men use hobbies not as a replacement for achievement but to have achievements they can appreciate rather than being instantly consumed without thanks and replaced with more demand. Compansionship is for our humanity and younger persons have had less of it beaten out of them.
That said, while rare, it is possible for a very self-aware and diligent person to allow the shit of life to push them into deeper connection with the beauty of life rather than have it beaten out of them. That kind of older woman is truly remarkable. Unfortunately, it seems they are most often mothers or nuns or something of the sort. Single women are often in some form of arrested development patterning after Sex in the City and whatever trash echo chamber they have on social media. The same can be said for men, though. But speaking of age-related risk factors here I am, a middle aged man starting early into my old man rants. Not sure they would be appreciated by a younger woman if I did ever chance it, haha.