The rise of Reform and the Bloc came with the demise of the PCs. It was a temporary fracturing, not a permanent state of affairs. Most of the time is definitely overstating it.
Long, possibly contentious argument:
The NDP falling apart helped as well -- people often overlook that 1993 didn't just see the obliteration of the PC Party*, but also the NDP, who went from 44 seats to 9 seats. I don't have the exact numbers off-hand, but a significant number of seats actually ended up going from the NDP to the Reform Party (I know this because in 2000, I was working in the PC Party research office, and I had to do riding profiles for every riding in the country). I know that sounds counterintuitive, but I once had someone explain it to me that Canada didn't really divide into left and right, but rather establishment and counter-establishment, with the bulk of the population falling on the establishment side (which falls in line with the whole POGG idea of Canada). The West was where the bulk of the counter-establishment was/is, so they went for the NDP when it was a viable protest voice, and they switched over to the Reform Party when that started seeming more viable.
* Also, I need to point out that the PC Party wasn't as thoroughly devastated in 1993 as the final results would have you believe. They still got 16% of the vote -- 2.5x more than the NDP -- but because of FPTP, their vote was too inefficiently spread out to show up in the final results. Not that it matters anymore, of course.
(Further evidence that Canada's not -- or, at least, wasn't -- neatly split on left-right lines: the BQ took a whole bunch of seats from the PC Party, even though they're supposedly on opposite sides of the ideological spectrum. This is similar to what happened in the West, since in Quebec, the PC Party was sort of the counter-establishment to the Liberal establishment.)
Obviously, Canada has clearly become much more polarized along left-right lines over the last twenty years -- people bought into the "Unite The Right" myth, so even if it wasn't true at first, it eventually became that way, and once it was established that we had a "right" to unite, then it became belief that the same could/should be done on the left. However, I think there's still a little something to the idea that Canada's more divided along establishment-antiestablishment lines than ideology -- consider the fact that while the rest of the world has seen incumbents losing on a regular basis throughout the course of the recent recession, incumbents here won more often than not, federally and provincially.
All of that is to say: I think that as long as we have a 2.5+ party system, the only way the Liberals ever get back to their former glory is by somehow reclaiming the centre, and establishing themselves as...well, the establishment party. It obviously won't be easy for them to do, seeing as the Conservatives have managed to keep a lid on/hide their craziness for so long that they've arguably displaced the Liberals from that spot, but it's pretty much their only chance. (As a sidenote, consider how the Conservatives have won the past two elections -- in 2008 they painted Stephane Dion as some crazy green radical, and them in 2011 they made Iggy out to be some sinister other. In both cases, they relied on voters not wanting to rock the boat too much, which comes straight out of the playbook the Liberals used for decades.)
So, TL, DR: there's no left to unite, and pretending there is just helps the Conservatives stay in power.
