It's not even clear that countermajoritarian institutions advantage conservatism in general, as opposed to providing temporary tactical advantages to some elements of the coalition. https://twitter.com/mattyglesias/status/1289234672963133440

SCOTUS, the most powerful countermajoritarian institution, clearly hasn't over the past few decades.

The biggest constraint over the expansion of the welfare state are fiscal concerns and the tax-aversion of the middle class, not the filibuster. On the other hand, the filibuster does completely protect blue state (esp public sector) unions from reform pressure.

Nor does the electoral college have a consistent bias.
Obama won the pivotal state in 2012 (Colorado) by 5.3% -- more than he did the popular vote nationwide (3.9%).

The pivotal House seat is maybe a percentage point or two more R than the electorate as a whole, but as we've seen that's easily overcome by a typical midterm wave against the President's party and probably still the magnitude of the incumbency effect.

Nor is the Senate significantly more R-leaning. The GOP hasn't once had a filibuster-proof majority since the cloture rule was introduced.

Blaming the rules is a time-honored way for establishment Democrats to excuse a failure to enact liberals' policy wish-lists. But many of the rules are actually pretty easy to change, and the unpopularity of the agenda items ultimately matters more.

n.b.: Being able to frame a polling question to make your policy preference appear popular doesn't mean that voters will actually feel that way about it when they learn about associated opportunity costs. Elected representatives understand and anticipate that.

The more sophisticated argument for why the constitutional structure skews conservative is probably Willmore Kendall's -- but one which *embraces* majoritarianism: https://www.jstor.org/stable/2108870?seq=1