The Swiss squad was one of the first to call time on any upgrades for last year's challenger, as it instead decided to focus all its resources on preparing its 2022 design for the new regulations.
But while it hopes that the work for this season will pay off, Vasseur has confessed that there were some negatives from not progressing with its 2021 car that he had not expected.
"We took very early the direction for 2022, at the end of '20," he told Motorsport.com. "And perhaps I underestimated the fact that we had 22 races to do with the same car.
"On the psychological side, it's not an easy one. When you have updates coming in or into the pipeline, you always have a kind of, not motivation, because the motivation is there, but hope that we will bring updates. And that was not the case."
Alfa Romeo eventually finished ninth in the constructors' championship last year, as Williams leapfrogged it, but Vasseur is clear that the change of form was not just down to performance.
"The pure performance was not bad," he said. "I think we did a step forward compared to last year.
"Looking at the average on the qualy, we were faster than Williams, our direct competitor. In the races, we were faster than Williams. We finished something like 14 times ahead of Williams in the race.
"But then, if you have a look at the classification, and this is the main KPI, we missed the two good opportunities of the season, in Budapest and Spa.
"I think Spa, we didn't do a good job in qualy, and by that way, we didn't score points. In Budapest, it's a bit more frustrating. We did a very good qualy, it was probably from a team perspective one of the best ones, as were on the sixth row or something like this, and we were involved in the crash at Turn 1.
"It would have been better to be as Williams, 17th, 18th in qualy. But it is like it is."
Despite some frustrations about what happened in 2021, though, Vasseur thinks the true answer about whether or not Alfa Romeo did the right thing will only become clear once the new season starts.
"We had a decision to take. Did we have interest to invest a lot of not just money, but time and resources and so on, on 2021? And what could be the expectation, to move from P9 to P8? Or do we put all our resources on '22 and then let's see, because I think the potential is much wider.
"OK, now it's done, we took the bet one year ago, and we'll see in a few months' time!"
