The thing that ultimately killed the G11 was the reunification of Germany. The end of the Cold War killed a lot of weapons programs. The G11 itself was a decent weapon and extremely reliable towards the end of the program. Some West German special operations groups had started field testing it before the program ended and the only real complaint is the same complaint that most small caliber weapons get: poor to mediocre terminal ballistics. The weapon itself and caseless ammunition still has its merits. If HK were to modernize the G11 to accept the accessories common on a modern fighting rifle (optics, lights, lasers, sound suppressors, etc.) and bump the caliber up to, say, 6.5mm-6.8mm (around .27 caliber) with an appropriately increased propellant charge, you'd have an excellent fighting rifle with good range and terminal ballistics. However, I think the next ammunition advancement for military rifles will be telescoped ammunition where the projectile is actually down inside the cartridge casing to make the ammunition more compact, along with a shift away from brass and steel for the casing towards polymers and lighter weight metals to make the ammunition lighter weight. The US military is already experimenting with this kind of ammunition design with the LSAT squad automatic weapon.
As far as pointless weapons go, my vote would have to go to PDWs like the P90 and MP7 due to the poor terminal ballistics of their ammunition. While they tend to have better range and flatter trajectory than a pistol caliber SMG, their rounds aren't very good "fight stoppers" compared to 9mm, .45 ACP, 10mm Auto, or .40 S&W due to their small caliber design and light bullet weights. A local SWAT team in my area was considering going to the P90 from MP5s and deciding against it after researching their effectiveness to stop a fight. It took many more rounds of the smaller projectiles to put a man down, sometimes as much as half a magazine (25 rounds), than a 9mm or .45 sub gun. They instead chose to go with all .45 caliber weapons and bought HK USP 45 pistols and UMP45 SMGs for their entry teams. This was quite a few years ago, 2006 or 2007 I believe, so I'm not sure if they're still using the same weapons.