Here's another article crapping on Toronto sports fans: When it comes to sports, Toronto is a city of losers
I agree with the notion that because the fans continue to come out to see the games, win or (as seems more likely) lose, the organizations behind the teams has no financial incentive to improve the on-field product. However, the problem isn't so much the individual fan, but the fact that there are so many of them that demand for the product far exceeds the organizations' abilities to deliver.
My favorite example of this is the Maple Leafs. The problem is that the fan-base in Southern Ontario is so wide that even if every fan who attended a game this year totally boycotted the team next year, the arena would probably still sell out.
Maple Leaf Sports Entertainment (MLSE) has a monopoly, in that they are the only ones who can supply regular access to games played by the Maple Leafs. Such is the demand that MLSE can demand high prices for tickets to those games; the surrounding market provides enough rich people who want to see the games that these games will frequently (usually?) sell out.
So consider what happens if by some miracle the Leafs are built into a contending team. How does this affect the box office? Since the box office sells out already, it doesn't. The fact that a winning team would increase the desirability of a Maple Leafs ticket means MLSE could conceivably raise prices. However the fact that there is a secondary market for Leafs tickets shows that MLSE is already leaving some money on the table.
The combined Southern Ontario market in general, and the Metro Toronto market in particular, is so big that any organization with even a moderate market penetration will find enough fans with enough money to keep them in business.
In a smaller market, say for example Ottawa, a losing team does become economically unviable. This will eventually run the ownership group out of money, resulting in a change of ownership, management, and eventually -- should the on-field product not improve -- venue. We saw it with the CFL several times, and minor league baseball has left Ottawa twice already too.
But Toronto's sports enterprises have such a rich market in potential fanbase that it is unlikely that you could measure a drop in fan support at the box office. As such, while the organizations want to improve for pride reasons, there isn't any financial mechanism to sweep out the ownership and management which has thus far failed to deliver.