37signals recommended functioning alternative services, not just data export.
(Actually, it wouldn't have mattered. Don't kid yourself.)
They deliberately gave a three month sunset for users to find another solution. That's entirely the point of a sunset.
Their product is also free, so it's not like they're hurting businesses or real customers by not helping them find alternatives. They're not really obligated to even do anything at all - it was a free service. If they were being paid it would make more sense.