Mercedes has remained loyal to the zero-sidepods concept on its W14 that caused such a stir last season.
Team principal Toto Wolff was adamant at the time the approach was not the root cause for Mercedes' performances last year.
There is an indication now, however, the team is unconvinced by the design.
The Dutch driver went on to clinch victory, finishing 51 seconds clear of seven-time champion Hamilton, with Russell a further five seconds adrift.
Speaking to Austrian publication OE24, Marko said: “Mercedes has more than one obstacle, that's clear.
“They have not made any progress compared to last season. If you look at the gaps, it was even a step backward.
“They seem to have lost their way somewhere.”
Mercedes development affected by budget?
This season the 10 teams have just US$135 million to spend, a drop of $5m compared to last year.
Mercedes at least knows it can develop a car over the course of a campaign in this era after starting slowly last year following the introduction of new aerodynamic regulations.
The W13 was badly affected by porpoising and bouncing over the first half of the season, in particular, before Russell went on to win the penultimate race of the year in São Paulo.
Marko is now “curious to see what they (Mercedes) will do now” when it comes to developing the W14.
“Because of the cost cap, it's such a problem to develop the car routinely,” he added. “How do you put together a completely new car?
“Unless they make a golden shot, which I wouldn't assume after recent experiences.”