I don't think that's the case at all. Arguably their biggest problem for the last half-decade or so has been messaging. Martin was always saying everything was an extremely important top priority, and as a result -- like the Economist said -- it was easy to label him as a spineless ditherer. Dion and his team were completely inept at messaging, and I say that as someone who joined the party because I liked him so much. Iggy could've/should've been an improvement, but he never settled into any kind of coherent theme, and that made it impossible for him to gain any traction. (It also didn't help that he didn't hit back at all over the "Just Visiting" ads.) At the very least, I think Trudeau should be a huge improvement over each of them.
That's not to say he wouldn't face some issues as leader. I don't know what kind of infrastructure the Liberals have left outside of the Maritimes and parts of Ontario, so he may face a huge challenge in reviving all the Electoral District Associations and making the competitive again. And, of course, he'd need to be ready to take on the Conservatives' negative ads right out of the gate; while the Liberals have been surprisingly successful at fundraising as a third-place party (I got a fundraising email a few days ago that said that they've consistently outraised the NDP every quarter since the 2011 election; if true, that's astounding), there's no way they can compete with the Conservatives financially, so he'd have to figure out how to respond strongly in a cost-effective way.