Once you’re accustomed to it, bicycling to work is not much exercise. It’s certainly better than nothing, but I would not see some mild cardio as a replacement for running and/or strength training.
The commute will become shorter due to increased speed, but that doesn't stop one from putting in more effort to maintain an even higher speed.
you can use it for strength training if you do a few sprints, but the main pull of it it that you don't realise you're burning many calories unless you really try.
breathing fresh air for an hour is great too.