We should absolutely blame MAB and Co. for chasing Jess off the show and marginalizing Jill. Jess has even said as much herself - she was ready to retire in 2012 after her contract expired, and she didn’t get the sense MAB and Co. had much value for Jill. MAB didn’t even try to keep her either or promise her a story either.
When MAB was canned that year, it was JFP (who Jess liked a lot) who reached back out to Jess and asked her to come back - Jess agreed, but only on recurring as she had already packed up her life with her late husband and moved to Oregon. Her status has been the same ever since.