It is harsh to blame the guys who are out there doing their best. Who's to say there are not maxing out their potential. Why should Beattie be sub 27:10 by now? 27:23 is about what I would expect. Don't blame the best guys we have got. They should be celebrated and encouraged. It's not their fault we as a nation are not producing elite 5 and 10k runners.
Eamon Martin and Jon Brown mentioned in other comments above were truly world class. Brown was Euro cross country champ, top 10 ish in world cross when everyone did it, 4th in the Olympics twice, Martin won the London marathon and frant ran 27:23 in Oslo to win the race. The current guys are not anywhere near their level so it is not surprising to me they can't run faster even with today's advantages.
I agree to a point about spending time at altitude but the main problem is a lack of numbers competing at elite level. The more guys we have the more likely we are to find a world beater. We have a culture through BMC etc. and the expertise and role models to generate world class middle distance runners. We don't have the same for 5 and 10k. There is not incentive when the qualifying times are so tough and even if achieved world athletics standard / quota we don't always take full teams. It's no wonder people stick to middle distances or turn to the roads.
We don't have an NCAA system churning out loads of sub 28 min guys every year. If we want to generate some top 5 and 10k guys we probably need some of the top 15 guys with good endurance to step up, keep the best we have in those events e.g. Marc Scott and a governing body that supports the level below the top elite. It takes years to get to your potential in longer distances. They think far too short term and support athletes that have already made it not the people who actually need their help. I don't see a structure or pathway for 5 and 10k runners.
10k track is a dieing as an event in any case. There is only one or two 10ks on the track with a realistic chance to get the world or Olympics (or Euros) qualifying time. Hard to think why many people would dedicate themselves to the event.