The real issue was offset compensation. The fact that the beta was highly temperature dependent wasn’t that major an issue because you could tame that with lots of feedback. It was really hard to get a pair with well-matched offset. There were a lot of designs that depended on close thermal coupling of a pair of transistors (usually tied to a common emitter resistor, the current mirror didn’t come along until later).
Vacuum tube op-amps were also common prior to that. Something like a 12AX7 made a nice differential input stage. Interstage coupling got weird, though.
