When Mulroney announced he would resign, he said
"Whether you agree with our solutions or not, none will accuse us, I think, of having chosen to evade our responsibilities by sidestepping the most controversial issues of our time."
30+ years later and I don't think there's any room to deny that. His government saw a lot of problems, a lot of which they thought (probably quite rightly, in retrospect) were inherited P.E. Trudeau mistakes, and they decided to face them head-on. Even if the end result didn't bear the fruit it was supposed to, what they tried to do was at least justifiable and seemingly in a genuine attempt to fix the issues of the day.
They desperately had to do something about the budget deficits that Trudeau's government incurred through the early '80s; in retrospect I think it can be argued they were on the right track, but didn't go far enough to get the results required. (Whereas the Chrétien/Martin Liberals basically did exactly what the Mulroney PCs said they'd do, and got a lot of credit for it.)
A lot people hated NAFTA then, and still hate it now, and the detractors were mostly correct about how it would slowly destroy the country's manufacturing base and move it to cheaper Mexican and fervently anti-union jurisdictions in the American South. However, I think in retrospect it would have happened with or without the deal. At least with the deal in place it happened in a somewhat slower and more predictable way. The destruction of the consumer goods manufacturing base would have happened anyway; every first-world country has the same problem. We collectively all off-shored our production of consumer goods to China; NAFTA neither caused that nor stemmed the flow.
The fire they ultimately never should have played with was re-opening Trudeau's constitutional debates in an attempt to iron out the mistakes and omissions with the Meech Lake and Charlottetown Accords. In the end it felt like a bunch of effete politicians were asserting to the rest of us what Canada is and should be. That Quebeckers and Western Canadians alike were the most ardent opponents in the Charlottetown Accord referenda was probably a more effective expression of national unity than the accord itself, haha.
That said, the fact that Mulroney's time in government ultimately ended up with the creation of the Reform Party and Bloc, and the PCs being decimated, is precisely why no PM we've had since has gone anywhere near those issues. Harper cut the GST, which in retrospect I think we'll find to have been shortsighted and merely an easy 'score' of political points, and tabled (and passed) the toothless "Québécois nation" motion in 2006, but no one has otherwise gone anywhere near the constitutional issues that Meech Lake/Charlottetown were meant to address. I doubt they ever will, in my lifetime.
It is amazing to go back and revisit the televised debates between Mulroney and John Turner, and see how far our political discourse has fallen in 40 years. I don't know if Mulroney was as "gentlemanly" as some people say—I've read several anecdotes from his political allies who said he was among the slipperiest, most adept liars they'd ever known—but at least on the surface they could have reasonable discussions about issues. Nowadays is more akin to a bunch of gibbons hooting and hurling excrement at each other...