Yes, it would have just been a bit more difficult.
As of DD, Anakin and Dooku were described as being evenly matched during their battle. By RotS, it's logical to assume that Anakin had improved even moreso(because that's just what he did.) However, even if we assume that light side Anakin and Dooku were *just* equals during RotS, Anakin had the benefit of youth/stamina on his side... So in a battle of attrition, he still would have ultimately won(assuming no external variables affected their fight.)
And if the RotS novelization is still a thing, it is also made clear that Anakin was indeed getting the better of Dooku before he ever even tapped the dark side:
And even now, [Anakin] was holding himself back; even now, as he landed at Dooku's flank and rained blows upon the Sith Lord's defenses, even as he drove Dooku backward step after step, Dooku could feel how Skywalker kept his fury banked behind walls of will.