Also, considering I make exactly $0 per month from it, it's either be patient or use another service that had more capacity and faster builders.

I believe that Travis-CI had a higher limit for parallel jobs, but your builds would most often end up queued because of a low capacity for a certain type of agents. Also, something quite noticeable was their lower limits on build time, which is why for some builds a cache was necessary. It got a bit hairy when you needed a full successful build to properly populate the cache but they would never finish in time. And of course, the biggest drawback from Travis-CI back then was the lack of Windows support.

As for Azure CI, I believe there's something like a 10 parallel builds limit. And I've got exactly 10 configurations!