The more competitions the better as far as I'm concerned, but I know the organisers won't necessarily agree! I like the idea of an "veteran's" classification - 35 and over perhaps. I have a feeling it might be treated quite light-heartedly, and at one time it would have featured Joop Zoetemelk and Lucien Van Impe battling toe to toe.
But I think young rider is more important and I hope to continues. A bit of history: it started in 1975 and until 1982 was awarded to the best-placed rider in his third pro season or earlier. The first winner was Francesco Moser who finished an honourable seventh overall despite a heavy crash in the second week, with five of the riders ahead being past or future overall winners, exactly the sort of result that would have been intended.
The winners under that system were all perfectly sound, and I'm not sure why it was changed. Perhaps Phil Anderson winning in 1982 having made a serious mark on the 1981 race was a bit hard to swallow, and for the next four years it was open to Tour debutants regardless of experience. Again, there doesn't appear to be anything wrong with the list of winners in those years, but second place for Angel Arroyo in 1983, an experienced Spanish rider coming to the Tour for the first time, does look a bit odd. However Lemond winning in 1984 instead of the all-conquering Fignon is far more satisfactory.
Maybe going back to the previous system so soon wouldn't have been a good look, but anyway the purely age-based qualification has been in force since 1987. The jersey itself disappeared during the 90s but the competition continued. Multiple winners like Pantani, Ullrich, Schleck and Pogacar started to emerge, making the competition feel somewhat irrelevant.
I'm not sure what was ever wrong with the "length of time in the pro peloton" qualification. It seems to be pretty unusual for the Tour to be contested by second-year pros, and if such a rider won the White Jersey, Fignon in 1983 being one example, you could always say that he's ineligible the following year, but I'm not sure you'd need to. Gimondi won the Tour as a neo-pro in 1965, and had the youth classification existed then he would have won it again 1967. That was truly exceptional, so is it a problem?