While the German manufacturer was buoyed by Lewis Hamilton taking the runner-up spot in the China sprint last weekend, it still endured a challenging Sunday race as it came home behind McLaren and Ferrari again.
But with no notable uptrend in its form despite the efforts it has made to better understand its W15, Wolff thinks that it has to lift its game rather than think that glimmers of hope are the reality of where it is at.
Speaking to Servus TV about his reaction to the Chinese GP weekend, Wolff said: "Not satisfied at all. Maybe a small highlight with second place in the sprint race, but the performance is not there.
"We can keep telling ourselves that there were bright spots at the weekend, but we have to take a step.
"We'll bring a bit of something to Miami, where hopefully we can expect something. But today you're just behind the Ferraris and behind [Lando] Norris. Just not good enough."
Mercedes has come into the year upbeat about the progress it has made with its W15, and its early conclusion was the platform was strong but had some weaknesses in high-speed corners.
However, as events have progressed, the team has uncovered more complications with the car, which makes it tricky to find the right sweet spot with the set-up.
As Wolff admitted in China, gains it has made with its high-speed characteristics were proven in Japan, but this progress was at the expense of its pace in other corners.
"I think we absolutely achieved that, in the high speed we were super competitive, also in Suzuka through the Esses, and it was day and night compared to what we had before," said Wolff.
"The drivers were speaking about it as the best car they had in the last two-and-a-half years. Then we really didn't perform in the low speeds.
"So you gain half a second in the high speed, but you lose half a second in the low speed. The equation is back to zero, so that is something we need to improve.
"We are beyond the point of understanding and we just need to improve now. That is what it needs to hop to, and we have all the facts on the table.
"We know what we tweaked in order to solve the high-speed, and we know where the car was before to be quick in the low-speed. Now we just need to bolt the car together that does both of them."
While Mercedes has failed to finish on the podium in a grand prix so far this season, Wolff does not think this year's car is worse than its previous ground effect machinery.
Instead, he thinks his squad was perhaps flattered before when rivals like McLaren and Ferrari were having their own competitive struggles.
"The advantage we had was McLaren was not racing us for the first half of the season, so they weren't a competitor," he said.
"Ferrari wasn't as quick and dropped the ball on several occasions and that's why we were a podium contender and closest to Red Bull.
"Now those teams have picked up their performance levels. This is a relative game and suddenly, what was good enough for third last year is now [only] good enough for sixth. That's why it is tough.
"The car is as difficult as it has been in the past, tricky for the drivers. George [Russell], when we discussed it [on Saturday], said it was the trickiest qualifying car he has had so far. So overall, in a way, the same symptoms."
