Rodgers is mid-table at best.
With a mid-table club with mid-table resources, he'll be a mid table manager.
With better tools, he's better than a mid-table manager. His record over 3 full seasons at Liverpool was:
2012-13 League position 7th (61pts)
2013-14 League position 2nd (84pts)
2014-15 League position 6th (62pts)
Average league positions of 5th and average points tally of 69pts.
For context the 3 seasons before Rodgers joined we achieved an average league position of 7th and an average points tally of 58.
There's obviously some context behind individual seasons but Rodgers on the whole improved our performance and league position, And before anyone mentions Suarez, he played in 2 of the seasons before Rodgers (albeit from January onwards in 2010-11) arrived and 2 season when Rodgers was in charge.
I suppose my real point is that Rodgers isn't as bad as you, and many others, have made out. He's not a top manager at the moment but he's certainly got the capability to be better than a mid table manager. Because it ended badly at Liverpool it doesn't mean he's useless.
Personally I hope he uses Celtic as a stepping stone to achieve some success and get back to one of the top clubs in England/Europe.