I'll defer to the experts, but the obvious thing is that they need Price to be Price, and they need better D, especially LD.
They need Kotkaniemi to evolve into a 70-80 point game-controlling pivot. I like Domi, but I believe his game has tailed off discernably since the hot start, and I have trouble seeing him as a #1C in the playoff grind. Guys like Poehling and Suzuki are obviously blue-chippers who will help, but then again they will be supplanting guys like Byron who will be entering the downside as they develop their NHL careers.
No matter how you slice it, it's hard to see them being built on anything other than the Vegas method of rolling four lines and contending due to depth rather than top-end talent. This is why significant upgrades on the blueline are so important. Right now, the Tavareses and Stamkoses of the world will make the difference in a long playoff series. I think this is partly because players like that can outclass everyone on our blueline except Weber.
The fact that Weber is 33 may also turn out to become a structural problem. It will depend on how he ages. But if his game slips a notch or two, that could make a huge difference to the prospects for this generation of Habs.