Nowadays the standards for CBs has gone up, previously people used to do more albums because 1 MV was enough but recently things has changed. NewJeans has released MVs for multiple tracks every comeback. IVE had Kitsch and After Like, now they will release 3 tracks for I'VE MINE. Lee Sserafim also promoted two tracks their last comeback. Nmixx did the same.
All of those MVs cost a LOT of money. Nowadays long promotion periods for CBs are the norm as well. More teasers, more money. Plus the standard for them has increased as well. Nowadays teasers are A LOT better than with 3rd Gen.
All of these costs add up so it makes sense for them to release fewer full albums and just do minis and EPs.