The thing is that by lacking an upstream community distribution being developed in the open (a tried and tested model used in Fedora/RHEL, OpenSUSE/SLES, Debian/Ubuntu) Sailfish OS is in a pretty bad position. Community can't help with testing and integration of new components, so it all falls back to internal Jolla developers, delaying library and toolchain updates further and further. This also effectively mean most components don't have a stable maintainer, so even if community members want to contribute improvements an fixes to open parts of Sailfish OS, it takes ages to get them merged. So while the community + stable/enterprise distro model is definitely not without overhead, I think Jolla is seriously risking it's future without using it - and without enabling more community involvement overall. It's pretty apparent at this point that both single-handedly maintaining it's own distro in a reasonably current & safe state without community help and also adding new features and hardware support is not really working out.
It comes to mind, the comparison Jolla/Apple also has some substance. The good part of apples success is presenting a consistant experience to the user. The propriatary bits of sailfish are mostly those that have direct influence to this red-line/UX. Imho jolla planned a trade-off between control over ux and not having the advantage of foss contributions in those areas. How this plan turned out with decreasing inhouse dev-force and community is another matter. Good intentions, crippled by (market) reality.