While Canada's Wonderland had its own equivalent, the Kingswood Music Theatre, and was the defacto outdoor venue for concerts in the Toronto area in the 1980s and the early to mid 1990s, it appears to my knowledge that the Timberwolf Amphitheater doesn't have an explanation as to why it's not still popular today for concerts.

What happened in Toronto was obvious, Ontario Place opened the Molson Amphiteatre in 1994 and no one wanted to go to Kingswood anymore. Ironic that Ontario Place itself has shut down except for the Molson Amphitheater (which is called the Budweiser Stage today). So what's the explanation for the downfall of Timberwolf?

The search feature is your friend...basically the same fate as at Wonderland...between Riverbend at Coney and other nearby city venues, Timberwolf has seen better days...