It is extremely common to for some posters to assess extreme airshow manoeuvres and to conclude they have no value in the context of the operational role of the aircraft and so dismiss them as gimmicks.
Such people are failing to appreciate that these routines have often been carefully designed to demonstrate (to insiders) the margins of handling, stability and control and engine operation that exist and surround the normal service envelope of the aircraft.
Some of the manoeuvres on this video say several things very loudly (to those who can speak the language). For example that the engine/intake combination has a surge margin beyond the normal running line that is ahead of many other contemporary fighters and the aircraft has no minimum speed below which the FBW system must necessarily act to prevent the aircraft going slower – which of course is an issue with unstable designs in close in combat.
It was the same with my Harrier displays back in the 70s when as well as just entertaining the folk queuing for ice-creams I was showing service pilots of the day the alpha and beta margins that they could relax inside when doing normal takeoff and landing manoeuvres.
BTW antic81 it is my understanding that the Su-27 was FBW from the off. The Mig-29 went FBW from the mid 90s