I once watched a documentary where it was claimed that Ikea makes more revenue from all the small items (internally called "satellite articles") than from furniture. It’s not surprising why one floor consists entirely of furniture display and an equally sized floor consists of small furnishing items.
However, you are fundamentally right in your criticism: the selection of system furniture has become smaller and Ikea prefers to use its shelf space for the self-service warehouse more for additional small furniture than for greater flexibility of Pax, Besta, Metod, etc.
Additional cabinet widths would be desirable, especially for PAX, at least a 30cm cabinet carcass for Metod, and even if only with an 80x30 front just for shelves. Besta should again offer the high-quality full extension drawers from Hettich, like the old Inreda had. Different heights of carcasses and fronts should also be offered again for Besta, as listed in the buying guide from the 2010 catalog.
The problem with the system furniture is that for an additional carcass along with a new front size they have to reserve 10 self-service warehouse spaces again to be able to offer it in all front colors.
However, Ikea has realized that they make more daily revenue per meter of shelf space if they offer many more small single pieces of furniture than a wider selection of system furniture. It’s also logical that you sell an armchair in a trendy color more often than a 30x80cm front of the Veddinge GRAY type. I am also convinced that Metod requires less shelf space than was the case with Faktum (there were 50cm sinks, tambour door cabinets, 30cm cabinets, drawers from 30 to 60cm in 10cm increments, 80cm), etc. However, the flexibility with Metod is still very good, even with Faktum there were inflexible compromises (50cm front on 45cm dishwasher).
Anyone planning with Metod has to rearrange somehow and manage it differently. The same goes with Besta or Pax. Still, one gets annoyed that one cannot arrange the furniture as individually as it could actually be possible. I think Ikea does not lose much revenue, only ultimately a few detail lovers buy from a much more expensive and more flexible system kitchen provider.
Ikea simply has a big data construct and can test in one country whether revenue increases when system furniture is reduced and replaced by small furniture, or when furniture is replaced altogether by satellite articles. If it works, they do it in all countries in the next catalog year.