They say cadets make better candidates for teaching how to fly multi-crew commercial jet aircraft. Undoubtedly true. Take any 18 year old and pit them off against a 45 year old, who is going to fair better whilst playing a video game? The young, keen, unadulterated nature of youth is always there ready to be exploited for maximum gains in efficiency whilst being able to offer an apprentice rate salary. Applies to most industries, aviation is not unique.
However, you are comparing opposite ends of the spectrum. It's hardly ever like this. If EZY were to add 10 aircraft to the fleet over the next year therefore needing to hire another 50 FOs, recent trends show they would probably hire 50 cadets instead of 50 type rated FOs with 2 years on the line (1,500 hours) who just got laid off. 10,000 hour non-type rated captains (ready and willing to accept FO positions) would not even be on the radar screen.
There is nothing terribly difficult about flying a modern airliner once you have the experience. If a pilot has 2 years+ experience there is nothing that makes them a worse candidate than a cadet with a zero houred type rating and 100% devotion when it comes to a new job opening. The former could be an ex-cadet from another airline that went bust but is now on the market. The current system means the former will have a very low chance of getting hired by the likes of EZY or FR as those airlines almost exclusively turn towards their partnered schools to hire pilots. So, the likes of Beazle seem to be advocating a system where experience works directly against employability.
So whilst cadet hiring has merits, the level to which two of the largest employers of pilots in Europe go about it results in a very disposable pilot community. When you were young, keen and had £84,000 lying around you were a prime candidate. Two years later with some experience and a set of expectations you are considered damaged goods. Cadet recruitment is 25% to do with finding candidates who can learn much more easily and 75% to do with finding the cheapest source of labour. Forget your misguided comparisons between cadets and old boys. Be more realistic, compare the abilities of candidates with a few years experience and cadets. There is not a major difference, except for a financial one.