None of us know what the band (AKA Noel) was truly thinking but there did seem to be a "That'll Do" attitude to many Oasis albums. I think Noel didn't really have the ambition after reaching the height the band did after Morning Glory and it shows, particularly post SOTSOG.
I always find Noel's take on the post MG albums interesting as they don't always seem to line up with what is commonly thought on here. It'd be nice to read more quotes on them (the Be Here Now stuff is the only stuff that is really sticking with me right now) but as I remember he sums them up something like this (feel free to correct me or add to it):
Be Here Now: A real missed opportunity. He didn't feel like he understood that he was following up a classic 1-2 and the expectations that came with it. A fair chunk of the material ('Don't Go Away', 'Stand By Me', 'All Around The World'...) was outtakes from the last two records that at the time he believed to be better than the stuff he was throwing away as b-sides, something he now regrets. Some of the other material was recycled old stuff knocked into shape and simply isn't very good. 'D'You Know What I Mean?' is the stand out good track. The mix on the album is shocking. Some of the decisions he made (track lengths, overdubs, ect.) were really poor.
Standing On The Shoulder of Giants: The best sounding record with the worst selection of tracks. He was trying to give the band a new sound but struggled with the songwriting process. Hates 'Sunday Morning Call' and thinks 'Let's All Make Believe' is underrated.
Heathen Chemistry: The band hitting the reset button. Contains some really great songs like 'Little By Little' and 'Stop Crying Your Heart Out'. Thinks 'She Is Love' and 'Idler's Dream' are underrated.
Don't Believe The Truth: Contains some more great songs like 'The Importance of Being Idle' and 'Lyla' with the former being one of his best. Thinks 'Part of the Queue' is underrated.
Dig Out Your Soul: A return to the bands bigger sound. He strongly rates 'Falling Down' as the bands final single. Admits that the album would have been better with 'Come On Outside' and 'Record Machine' but solely blames Liam for them not getting finished.