There's quite a performance jump between RB211-535s on a 752 and CFM56-7 on a 738 (40,000lb -E4 vs 27,000lb -7B). Even with PW2037s the 752 has 36,000lb donks under each wing.
Look at the A340-200/300 which was massively undergunned with CFM56-5s (31-34k lb) - the 53,000lb Trent 500 on the 500/600 models is just in another thrust class completely.
Makes one wonder how things would have turned out if the A342/A343 had been made with RB211s instead of CFM56s... would climb performance been as derided as it seems to be at present?