Describing what is or isn't a pillar of the format is certainly difficult, but I think that Smmenen's comparison of Workshop and Gush as pillars does not accurately describe the metrics that make something a pillar. Pillars hold up their own section of the format, and in tandem with other pillars allow for an equilibrium to be reached. In other words, to be a pillar it is necessary to provide structural integrity to both the surrounding archetype and the format as a whole. Gush is ultimately one of many blue draw engines in the format that have come to define blue decks other the years when unrestricted (although Gush does lend itself to a certain style of blue deck). I think that there was an argument for Gush as a pillar of the format prior to Mentor and the Delve spells, but these cards in particular have blurred the line between the Comer and Weissman schools. Gush is no longer a defining feature of these decks as it was in RUG Delver or UR Pyromancer, but rather just another part of an amalgam of blue card advantage/velocity spells. Gush no longer supports a distinct archetype as it once did, but rather just made the best blue deck better by being unrestricted.
Conversely, I believe that Workshop is still necessary for the artifact prison decks to be viable, and that these decks provide an important check to other parts of the format (mostly fast combo).
This post is really not meant to address Aaron's post though, because he put quotes around "pillars of the format" almost as if to distance himself from the actual meaning of the term.
I too dislike that there is a need for this detente between the format's best decks to avoid one of them taking over. I still think the best way to solve this is to create some kind of replacement for Workshop that allows the deck to survive even if shop becomes restricted. This would relieve a major pressure point of the format that would hopefully not need to be counteracted given that shops decks are currently ahead in terms of metagame share and perhaps power level.