Judging simply by the rate of 'helpful' to 'unhelpful' votes on Jamor's latest Stellaris forum post, the team's reluctancy to throw more builds at the the QA department hasn't upset the fanbase too much. They're working on it, though; and the acknowledgement is enough for most people.
Without following the Stellaris fanbase too much, it's hard to understand the plight within. the game's project lead recently took to the official forums to explain that while a number of bugs are still present within the 1.6 Adams update, they're not done patching them out - despite the time required to do so.
"I just want to take a moment to try and clear up the speculation about our future patching plans. I said before that we are not done with patching 1.6, and that is still true. We will fix more of the reported issues and get them in to your hands before the next DLC."
I want to let our QA focus their resources on a single build at a time, so they've been on the experimental multiplayer beta in recent days. Split focus and multiple versions is a good way to introduce complexity and miss bugs. However, I will push a patch with more fixes in the next few weeks once QA resources to verify it are freed up again. As always our objective is a balance between quality and speed.
Rest assured you have not been ignored and we're going to get it to you when our resources allow."
Stellaris Project Lead
So that's the official explanation! Sure, single-player may be harbouring a few little bugs for now - but they're there through the idea that the people want their multiplayer fix! There's every possibility Jamor could flick the switch on a bugfix patch right this very second, but without throwing it to the QA team to test out first, there's an even greater chance of it causing utter devastation the moment it's released.
Patience is key, everyone. Give it a few more weeks and you'll have both multiplayer and a stable single-player. Likely until 1.7 comes around, at least. Grand Strategy is hard.