The weak era concept is absolute schite. There are evidently stronger and weaker times, but the difference is much lesser than some people think. This is evident from the way Federer and Djokovic suddenly weakened after AO '10 and RG '16 respectively. As soon as they get a bit worse, hitting the ball just a bit less deep and strong, many players are glad to have a go at them - that's how small the margins are. Tennis is an extremely tough sport, one of the toughest around, and any pro must be given full respect for their efforts (unless they deliberately refuse to try their best, i.e. tank intentionally - that is not respectful at all).
The only actually weak wins, in my mind, are those when one's opponents (potential opponents included) perform way below their best due to physical - and sometimes mental - issues. Federer had a weak final and overall a rather weak draw at AO '06 (Safin, Hewitt, Agassi down with injuries, Nadal absent, Roddick in a slump), but a strong QF vs Davydenko (which turned out to be "the real final") saved it. Djokovic had a weak draw to the final at USO '16 (Federer missing, Nadal way down, every second opponent retiring), but a strong final vs Wawrinka saved it. Still not weak enough.
Even actual finals vs injured opponents still count, however much it sucks. You can't discount a player's on the basis of his opponent having the misfortune of getting injured. That's part of the game, players must look after their health... Wins like Lendl's AO '90 and Nadal Madrid '14 still count in the record books without any diminishing factor, much to the chagrin of the weak era theorists. Lucky wins, sure, but nonetheless.