Three visits in 23 years is not a huge number of visits. How about a visit every so many months?
Given the number of charities the royals support - around 4000 in total a visit ever few months would mean 4 a year and that would mean 16,000 visits along with all the other duties.
It isn't feasible at all.
The Queen hardly ever visited any of her charities and that applies to all of them.
Camilla has 90 charities but she doesn't visit all of them every year. Charles has around 400 charities and again they don't get a visit every year. Edward has around 200 but the vast majority of his engagements are to do with only one - Duke of Edinburgh's Awards.
Personally I take issue with the younger generations claim that they'd have only a handful of charities so they could be "more involved"...whatever that means. I don't really feel like they're any more involved than the royals that have boat loads of charities...or at least involved on a level that provides solid justification.
If we're honest with ourselves there's almost zero need for 4,000 some odd charities to have a royal patron. Sticking with a more modest amount (say under 50 plus military stuff) for the average royal would work...visiting once to twice a year or as needed by the charity in question. Of course for the monarch there's another set of charities that have had the monarch as patron for several monarchs in a row...or the Queen whether regent or consort...that's slightly different.
As royals either retire, die, or are fired it's a good time to evaluate the need and effectiveness of having a royal patron for each affected charity...and which working royal would be a good fit. It's my opinion that as the BRF reduces it's official working members we will see a dramatic change to the number of patronages...but hopefully with the "more involved" to back up the change. Non working royals, just like nobles or celebs, are welcome to support however many charities they want with their own time.