(over 11,000 built) from the late 1930's until October 1945. By comparison, there were only 7300 or so lancasters produced.
Well, you could read so much into that...
They started building Wellingtons a lot earlier than Lancs so 'course there were more made (I'd have expected the difference to be greater given the Lanc's late arrival in comparison).
So many crashed (EFATO was often fatal) that they had to be replaced.
The Lanc was far more effective so fewer were needed.
The Lanc was a far more sophisticated bomber so took longer to produce.
Etc, etc.
It's a bit like the old saw that BoB was won by the Hurricane, not the Spit since far more of the former took part. True, but only because the RAF didn't have enough Spits at that time!
Sorry, the Wellington was 'all we had', but that doesn't make it particularly good.