This is going to be pretty rough but;
60s - 1 - 10 anime series per year
70s - 10 - 20 anime series per year
80s - 20 - 30 anime series per year
90s - 20 - 70 anime series per year
----- Lots of short 5 minute per ep series pop up here
00s - 50 - 150 anime series per year
10s - 80 - 170 anime series per year so far
Of course there are also films, specials, stand alone OVAs, recaps, music vids and whatever. These are things which take a few minutes to a few hours to watch and you are giving them the same time as full series. I wonder what the actual average amount of episodes for pure tv series would be, the 00s and onwards trend of 1 cour shows would have lowered it dramatically, it is safe to say that 30 eps per series is too many, or it is at least getting that way.
I don't have any figures for how much is translated but it is less than you would think. Although even if you watched everything, with or without subs, even if you hated it, it wouldn't take anywhere near 5000 years.
I get and agree with your point though, there is a huge pool of anime out there so people needn't rely on the current season's offerings.
Just waiting for GATE and Overlord to come out.
When I saw the announcement I knew that this would be right up your alley. No interest in reading the manga but I'll probably give the anime a shot, and then drop it after 5 minutes.