The number of events at Diamond League meetings will reduce from 32 to 24 next year, officials from the IAAF announced on Monday.
In a year-long review, the international athletics governing body also decided each meeting will scale down from two hours to 90 minutes.
There will be just 12 Diamond League meetings as opposed to 14, and only one season finale from 2020.
And the longest distance track race will be 3,000 metres.
“We can make the Diamond League even stronger and more relevant to the world our athletes and our fans live in today,” said IAAF president Lord Coe.
The new season, which starts on May 3 in Doha, will be the 10th edition of the competition.
American athletics coach Steve Magness wrote on Twitter: “Way to shoot distance running in the foot. It’s a missed opportunity to figure out how to connect to the masses.
“Your most viable potential audience are the people who do road races, park runs, etc – 5k is a universally understood distance. Figure out how to connect versus alienating your audience.”
Great Britain’s Dai Greene, a gold medalist in the men’s 400m hurdles at the 2010 Commonwealth Games and 2011 World Championships, was unhappy at the reduction in the number of Diamond League events.
He wrote: “It’s hard enough to get into top-scoring Diamond League events and in 2020 the IAAF are planning two less on the circuit.
“Getting into races is so often who you know, agents helping out their mates etc – and now this influences who attends a championship.” –IAAF