My DS has a shortened and kind of cutesy name and honestly, I have regretted the name so many times precisely because of the attitude of people like the OP. The thing is, when we were naming them we really didn't like the long version, and still don't, but the shorter version sounded cute for a toddler, kind of rakish for a young man and fine for an older man. I can also think of several famous adults who are known by the shortened version, despite being given the longer name and I think it suits them.
I do have regular wobbles that it isn't serious enough, but when DS goes for jobs he will likely be up against/interviewed by people with similar names, as they are so fashionable at the moment. He could also change his name by deed poll to the longer version simply for professional purposes if he felt his name would hold him back.
Lastly, as the OP is clearly making class based judgements- last time we went to a National Trust property I was struck by the number of seemingly middle class families whose children were almost exclusively called "cutesy" names. My DS was one of four with the same name. There's a chance they will all have longer names and as adults will go as Archibald, William, Frederick, Margaret, Cecilia and Matilda etc but I imagine a lot of them will stick with the shortened versions so the OP will likely come across plenty of middle class people going as Archie, Billy, Bill, Freddie, Fred, Maggie, Cece and Tilly, for example.