The reason you should make your own is that you can decide what you want it for, what is useful for you and what you want to know etc. You can also look at the information you are recording and setup the sheet around that. That way you’ll end up with something simple to use and clear in it’s output that might actually be useful. Rather than something that’s a pain to input data to so you don’t use it for long and has an overly complicated output so you get no real benefit from the information.
If you only record time and distance then anything more complicated than a mileage and pace log will be largely useless for you. If you have altitude, temperature, calories, average heart rate etc, you might want something more complicated.
For example, you might ride road and mtb and want some sort of equivalence output so you can track your training taking into account which bike you’ve been on. Eg average MTB speed is 11mph, average road speed is 18mph, so have an output where mtb mileage is multiplied up to an 18mph average. Then you might want to factor altitude gained into the equivalence and reduce the 18mph based on how much climbing you do.