My experience,
Cycling has a lot more stuff involved than running, especially performance-oriented cycling. There's the gear and maintenance of it, route planning and traffic, weather is more important, and there's also a lot more skills involved -- such as bike handling, especially in criteriums which are the most common low-key races around here.
If you want something that's a physical effort analogue of a running race, you need to find hill climbs or time trials, I don't know where you are in the world but it's slim pickins here in Mississippi. The criteriums are much more punchy and twitchy than any running race, and also very dependent on bike handling, skill, luck, and having massive balls. If you're racing just as a way to test your fitness and progress, you're going to get more than you bargained for.
I never stuck with it because I didn't like all of the overhead and complexity. Until Zwift.
I know indoor cycling sounds lame, but Zwift eliminates almost all of the complexity and overhead involved in cycling. It makes it much more of a pure test of fitness. Aero doesn't matter, gear matters much less, no bike handling, traffic, crashes, can safely ride when it's dark out or any weather, races available at basically any day any time. There is always a group riding at any given speed following "robo pacers" that you can get a base ride with, or you can do structured workouts. It even has clubs you can join and do things like team time trials or league racing.