The width of Burnhamthorpe through MCC should be viewed as a boon, not a detriment. It's easy to write it off as wholly anti-urban from a downtown Toronto-based perspective, but urbanity isn't everything - it's incredibly flexible when taking into account potential for rapid transit and public realm improvements, as well as street parking like mentioned above. We already saw that it was going to be used for a section of the downtown loop of the HuLRT, which would have reduced the lanes to 2 each way for that brief section between Duke of York and Hurontario. The downtown loop will most certainly re-emerge as a later phase and make use of the road space. Also, since MCC will most likely not get a GO spur in the forseeable future, it wouldn't be out of the question to suggest that a proposal for an HuLRT spur along Burnhamthorpe to Erindale GO could emerge eventually.
The green space along the south side of Burnhamthorpe is definitely reminiscent of tower-in-the-park, but that's all space that the public realm can use anyway. It's better to have space and not need it, as opposed to needing it and not having it. It's easier to fill empty space than it is to tear things down for new space. Fortunately, the density on the north side will be significantly more than the south side, with both Exchange District and the Oxford development. The current state of density in Toronto makes important transit projects and public space more expensive. What Mississauga has at the moment is not all that great from a traditional urban perspective, but it positions it well for growth in the future.