Blizzard made some changes to the Mentor Program in Dragonflight.

If you would like to become a mentor and help newcomers in Dragonflight, you must earn Level 70 and complete 3,000 quests (up from Level 60 in Shadowlands). The requirements remain simple and not convoluted as it was the case before Shadowlands Patch 9.1.5 where you had to earn multiple achievements to qualify.