No, Another Perfect Day (mainstream rock) and Low (Pantera fanbois) were not any move to the mainstream.
Honest.
I don't know what strange, alternate universe you inhabit, but there isn't one track from Swansong that is ever going to trouble the mainstream consciousness. You won't ever see it on guitar hero. They will never play it over the tanoy in your favourite mall. They will never use any of those songs to advertise a product.
Catchiness and simplicity of song writing does not equal mainstream, and even if it did, does it matter as long as the song is good ?