Nonsense. By what metrics do you consider it “the leader”? Popularity forced by marketing? I don’t know a single serious language learner that swears by Duoling

Nonsense. By what metrics do you consider it “the leader”? Popularity forced by marketing? I don’t know a single serious language learner that swears by Duolingo. My gf, who spent at least 100 days on Duolingo, migrated to Babbel.