I took up cycling as an alternative to running, which i took up 2 years previously as couch-to-5k when i was super unfit couldnt run 100 metres and a 5 mile bike ride would be serious effort. Nothing bad to say about running and enjoyed 5k/10k/HM races trying to get in the top 50% as a superheavyweight was a good challenge.

Lost motivation though really with nothing to aim for, couldnt sustain or improve speed or distance without a lot of running time each week, so i started cycling more and totally neglected the running.
The same kinda things happening with cycling though, im not getting any faster than 14-15mph avg. on a hybrid (700c hardtail) that feels as aerodynamic as a parachute if i try to go faster and ive got used to 30-40mile rides being easy. I plan to try 60/80/100mile routes when the weather gets nicer, but still feels fairly pointless as i dont see me sustaining it.
I mostly cycle for weight loss and balloon if i stop the exercise, mainly because i replace it with snacking. Ill keep it up and ill enjoy it in the summer, but in relation to this thread ive kinda lost motivation for fitness since im not getting gains and havent got goals.