That's what I don't understand. They could mitigate their name so much if they just split free/paid/enterprise. It's already shown that enterprise is much more estable and is largely unaffected from service disruptions. Why don't they go one more layer? For sure it's worth the extra complexity.
Depending on the cause of the current issues, that move would likely cause more harm to paid services than good.
Their last postmortem made clear that their challenges are operational. Scale puts pressure on operation, but it's not what blocks them from keeping up.
Doubling the operation doubles the operational challenges.
There is no such thing as "just split" there is 20+ years of legacy decisions and even if the split is relatively clean it is still probably 1 years work for 200 people for maybe a marginal improvement.
The real money is going to go towards, "make this all more reliable".