Why a better MiG-15 engine might arrive too late

Would more Soviet work on axial-flow compressors necessarily give the MiG-15 a better engine in time?

Possibly not: the engine might improve, but the extra development could delay it until after the period when it was needed.

More research into axial-flow compressors could have produced a better Soviet engine. It could also have taken longer, leaving that engine unavailable when the MiG-15 needed it. Improved performance would therefore have to be weighed against the development schedule.