The best software for transport diagrams/maps?

Hi everyone, I'm currently using MetroMapMaker to make my diagrams and maps (of fancy cities from Listenbourg). It's good software overall, but I find it lacking in functionality (impossible to create correspondences, or I don't know how to do it, and you're not really free in the design of lines, for example when you want to create curves or right angles and it fills unnecessary spaces). That's why I'd like to try something else. I recently saw a video of a guy who redrew the map of the Oslo metro on Adobe Illustrator, and I know it's one of the best programs for making diagrams, but the subscription price makes me wonder, is it really the best program, and what are the alternatives (both on the web and in software)?