because of the oil crisis back then, Alfa and Alpine weren't really ready to start with their 12cyl or turbo engines.
Matra withdrew after 74, Ferrari after 73 already.
The 5 Litre monsters by Porche and Ferrari were banned since 72.

So Gulf Mirage stayed, and wiped the floor with the privateer cars, oldies like the 908/3 or GT derivates as the Ligiers.

Still, it is in the history books, and the cars are cool.
Same for 74 CanAm or 1976 Gr5 and Gr6 racing.
Mediocre races, dominating works teams, amazing legendary cars.

https://www.goodwood.com/grr/race/historic/derek-bells-first-le-mans-victory-50-years-on--frankels-insight/