While 2023 was dominated by Max Verstappen and Red Bull, McCullough suggests that in the third season of the current regulations, the top teams will be closer together.
He cited qualifying for the final race of this year in Abu Dhabi, where eight teams featured in the top 10, as a guide to the direction that the series is taking.
"If you look at the fact that there were eight teams in the top 10 and how close qualifying was, that's phenomenal, isn't it really?" he said.
"And it just shows you that with stable regulations there's always an element of convergence.
"Some teams have developed really well this year, but I think they'd be the first to admit they started badly as well. So I think next year, it's going to be fantastic for the sport.
"I think trackside execution is going to be important, and I don't think the margins are going to be enormous.
"But everyone's trying to get that extra 10-15-20 points [of downforce] more than everybody else because that just gives you the advantage on track."
McCullough acknowledged that Aston Martin won't be able to repeat the progress it made over last winter when it went from seventh in the world championship to battling for podiums from the start of 2023.
"Obviously, I think it's helped when you weren't as strong last season to make such a big jump," he said. "And if we were to make the same jump now, we'll be well ahead of Red Bull, which is not going to happen!
"During last year we were developing the car, and by the end of the year, we were actually a lot closer to the fourth fastest team. So yes, we were closer to the front. But the jump wasn't as big if you look at the end of 2022, really."
McCullough said that Aston Martin's own target to is to have a car that is competitive at different venues without having to make major specification changes.
"We're trying to put a car together that you can take to all the tracks and just change the rear wing level, front wing level, and bang, be strong," he said.
"At the moment, we're having to sort of change components a bit, whether the bias is towards low-speed, high-speed, efficiency, etc. So that's why we've been changing some components from event to event.
"The aim next year is to have a car that you don't need to do that as much, and the base level is just higher.
"I think the learning from the tests we've done with components, and also the physical track testing of certain parts, has given us really good knowledge to help develop the car."
