The Soviet Su-15 Flagon had roughly the same performance. It was in service until the 1990s. It was considered to be pretty effective.
The MiG-21 was still effective against the Phantom over Vietnam. The Su-15 basically uses two of those engines and comes with an integrated radar. It was the backbone of Soviet air defense units until it was replaced by the Su-27 and MiG-31.
So I think the Chinese J-8II, roughly similar in layout but with more modern radar, was a competent design. Problem is it came out way too late.