The open letter may not have asked for that, but I certainly have seen the sentiment be expressed by a number of people over the last couple of years.
Almost exactly the idea of pausing development of all new content (because it's inevitably going to be half-baked and feel tacked on), until the base game is fully stable. Usually in relation to networking, instancing or PvP balance and/or "fixing" combat logging, in turn usually meaning they want FD to stop making new content until they abandon P2P instancing altogether.
Many of us wanted the half-baked stuff fully cooked before adding new stuff, yes. Give us more varied and interesting missions, fix broken and half-baked multicrew, make PP great (not again, as it never was), etc. But this would itself add NEW CONTENT. Heck, a revamp of the mission system along with improved CGs would add a huge amount of content.
The problem is that some of you confuse new ships (that includes the overhyped Fleet Carriers that most of you will be bored with in a month) with new content. Even atmospheric worlds, which I'm excited about, will become just as boring as airless moons if we're hamstrung by the same limited, repetitive, soulless mission system we currently have.
As for bugs, my personal complaint is that Frontier has prioritized silly stuff (like the color of cockpit panels of the DBS or the wires hanging down in the Anaconda) over the game-breaking things like crashes, broken menus, rubber-banding in Open, etc. And while I'm not one of these anti-Arx guys, I do think that bug fixes should have come before Arx. As long as the game feels broken and half-baked, I'm not spending more money on cosmetics, regardless the currency.
