What is Ironic complexity? What are some good resources to learn about it?
Here is a quote from Scott Aaronson's survey on the P vs NP question, in which he coined this term:


  There is one technique that has had some striking recent successes in proving circuit lower bounds, and that bypasses the natural proofs, relativization, and algebrization barriers. This technique might be called “ironic complexity theory.” It uses the existence of surprising algorithms in one setting to show the nonexistence of algorithms in another setting. It thus reveals a “duality” between upper and lower bounds, and reduces the problem of proving impossibility theorems to the much better-understood task of designing efficient algorithms.


The survey contains some pointers which you might want to look at.

Ryan Williams has given a series of two talks on this recently at the Simons institute: part 1 and part 2.