The 27-year-old is switching to the DTM this season to drive the new Ferrari 296 GT3 run by Emil Frey Racing. He spent the past two years with the Swiss outfit racing Lamborghinis in GT World Challenge Europe and ADAC GT Masters.
Aitken will have to miss one DTM round due to a clash with his prior commitment for Cadillac in the IMSA SportsCar Championship at Watkins Glen, but told Motorsport.com that learning a new car and series would have made a championship challenge tough even if he was contesting every race.
Instead, he's seeking to "try and get some wins under our belt" before the end of the season, which begins at Oschersleben on 27-28 May.
"I think fighting for the championship will be very, very difficult – also because I have to miss one race," said Aitken, who will be replaced in Zandvoort by team regular Albert Costa.
"Zandvoort clashes with Watkins Glen. But regardless, it would have been difficult.
"The fact that we have a new car, and BoP will always be conservative with a new car, and DTM is quite unique as well even if we're taking the ADAC organisation that we know means there's still going to be a learning curve for the team and for me.
"So I think if we can get to a point mid-season, end of season where we're winning races, that would be pretty mega."
Aitken said that from his experience in testing, the ORECA-built Ferrari was "more compliant" than the Lamborghini Huracan GT3 he previously drove.
Costa underlined the car's potential by qualifying second for the opening race of last weekend's GTWCE Sprint Cup curtain-raiser at Brands Hatch before a difficult pitstop dropped the car back.
"It helps that we're the only team there so of course there is more attention on us [from Ferrari]," he added.
Asked if he would derive any benefit from previously competing in GT Masters following the ADAC's takeover of the championship from ITR, Aitken replied that the main gain was from his previous experiencing of the "more obscure" tracks on the calendar.
"Oschersleben, Lausitzring and Sachsenring, they're not really places that you drive unless you're doing these German GT championships," he said.
"So to have done that last year is going to be really helpful I think.
"And otherwise just dealing with cold tyres, because you're also not allowed the tyre warmers in GT Masters. This year obviously we all put new tyres in the pitstop as well, where in GT Masters you carry on with hot tyres.
"I think everybody in testing is agreeing it's quite challenging, especially in the start of the year when the temperatures are still 10 degrees or so, it's pretty sketchy."
Formerly a Williams F1 reserve driver, Aitken made his sole F1 race outing at the 2020 Sakhir Grand Prix when George Russell was called up to Mercedes to replace a COVID-stricken Lewis Hamilton.
