The Frenchman claimed his maiden world championship at the Emilia Romagna Grand Prix at Misano two years ago after a crash from rival Francesco Bagnaia handed him the title with two rounds remaining.
But Yamaha has struggled since, and though Quartararo finished second in last year's standings, he is currently 11th, 178 points behind Ducati rider Bagnaia.
Quartararo has repeatedly aired his frustrations at Yamaha's lack of competitiveness, saying the current bike is "practically the same" as that which Jorge Lorenzo raced to the title in 2015.
Speaking ahead of this weekend's San Marino Grand Prix, Quartararo expressed his dismay at the team's position two years on from his title aged just 22.
He said: "Of course, it's a great feeling, but also it hurts to see where we are right now compared to two years ago.
"Of course, it was one of the best days of my life here, but going back to this place and knowing which position we are now, it hurts, but it is what it is.
"We have to think positive, try to bring Yamaha to the best position they can be, and hopefully being back here with the greatest feeling as 2021."
Quartararo finished seventh in last Sunday's grand prix at Barcelona, marking his best main race finish since he achieved the same result at the French GP.
He switched back to using last year's base settings, which he said did "help me quite a lot", but did not seem confident about carrying that positivity into this weekend's races.
Asked whether he had reasons to be more optimistic this weekend, Quartararo said: "Well, not really, it has been a tough weekend for us. Sunday was great, we went back to a previous setup, basically last year's base.
"It was a bit better, so basically here we don't know which one to start, so in FP1 we will do it with both and see how the weekend goes."
He added: "To be honest, going in, we have lost every year a little bit of our turning and this year we are missing it even more.
"With last year's base, it helps me carry a bit more speed and especially in Barcelona the grip was really low, it helps me quite a lot."
Monday's post-race test at Misano will be important for the marque's 2024 bike, with test rider Cal Crutchlow having given the latest model a shakedown at Aragon this week in preparation.
Though Quartararo said he had spoken to the Briton on Wednesday about the bike, he kept his cards close to his chest about Crutchlow's feedback.
