Fighters are classified by generation, as explained in [this answer](https://aviation.stackexchange.com/a/44920/3394). Given this [Wikipedia sum up](https://en.wikipedia.org/wiki/Jet_fighter_generations#Comparing_categorizations), some fighters are not clearly in a defined generation, especially for 4th generation subclasses. Thus people may not agree on a list of fighters that belongs to a generation.

Some of the previous generation (generation 4, 4+, 4.5, 4++) are still actively produced (e.g. Rafale, F/A-18E/F)  while the [F-22](https://en.wikipedia.org/wiki/Lockheed_Martin_F-22_Raptor) (definitely 5th generation) is no longer in production.

Airframe designed a long time ago (e.g. the F-15, F/A-18) still receive updates that make it competitive on international market (the section about [potential operator of the F/A-18](https://en.wikipedia.org/wiki/Boeing_F/A-18E/F_Super_Hornet#Potential_operators) on Wikipedia give an overview for the F/A-18), even in front of 5th generation fighters ([at least in Canada](https://www.popularmechanics.com/military/weapons/a24012/canada-f-18-order/) for the F/A-18 and the F-35)

Another capability we cannot rely on to define generation is stealth. The [A-12](https://en.wikipedia.org/wiki/Lockheed_A-12) and more precisely its variant [YF-12](https://appel.nasa.gov/2013/03/28/this-month-in-nasa-history-the-yf-12-blackbird/) was stealth supersonic aircraft with [weapons (AIM-47) inside internal bays](https://en.wikipedia.org/wiki/Lockheed_YF-12#Specifications_(YF-12A)), but was not a 5th generation fighter.
Moreover, since [ECM](https://en.wikipedia.org/wiki/Electronic_countermeasure) can be [fitted on a fighter](https://en.wikipedia.org/wiki/Thales_Spectra), this fighter expose some stealth feature.

Given those facts, it seems that since the 4th generation, knowing a fighter is classified as a specific generation does not provide information about its production year, its capabilities nor its competitivity in front of other nation's fighters.

What information does the generation of a fighter give? How useful it is to know a fighter belongs to a specific generation?