Lots of wrong in this thread.
1. There are no relaxed weight requirements for Navy or Air Force. Every Middie, Zoomie and Cadet has to pass a PT test in the Spring. Your PT Test results factor into your class rank (which is the predominant factor in getting your Service Assignment when you graduate). Back in the day, there was a max weight. It varied between 280-285. Guys would have to cut in the Spring semester to get under. That has been swapped out for body fat percentages--at all academies, including Coast Guard.
2. I'm not sure how Navy relaxed academic standards, but Army hasn't. Nearly every football player goes to the Prep school for both programs. Lots of guys who otherwise wouldn't have been NOMINATED--you aren't just offered a scholarship, you still go through a process--end up at both Prep schools.
Army's football woes come down to a handful of things, some of which Saran gets right above.
On the field, the most noticeable difference is Navy is better coached. Paul Johnson was on the staff when I was there--he coached the fullbacks (yes, they had their own position coach). Buddy Green has been on the staff 14 years Johnson coached Ken at Hawaii. There has been consistency of the staff for close to two decades.
The idea that the Army experience is more difficult than the Navy experience is dumb. There is no institutional culture that makes one harder than the other. Any plebe experience is 100% dictated by the upperclass leadership (cadre). If your cadre sucks, your plebe year will suck.
Army being "harder" than Navy is a myth propagated since US Grant was a plebe. Academically, it's not really close. Go look at the list of majors. Lots of majors you can go "hide" in at Army. No sociology, psychology majors or art history majors at Navy. The core requirements of every student are also much different. Every student at Navy is a STEM student, regardless of major. That means math through Calc 4. It means multiple lab sciences. It means mandatory engineering courses. Additionally, if there is a deficiency in the fleet in certain specialities, you can have your major changed to meet the needs of the Navy--pretty much no questions asked. You want to major in Economics? Yeah, well we need electrical engineers--have fun. Pretty sure that doesn't happen at Army.
Army's biggest issues are a failed experiment in C-USA and about 10 coaching changes in the last 25 years.