It’s not so much about being unable to do something it’s more about time available, priorities, childcare, choices and money.
just say you spend (every week)
56 hours sleeping (including one lie in)
42 hours a week at work including
commuting,
10 hours getting yourself ready in the morning (shower breakfast hair etc)
10 hours making and enjoying an evening meal
12 hours on household tasks including shopping, paperwork and general organisation
15 hours socialising
10 tv/web/reading
13 hours left for hobbies/family/relaxing baths.
With kids
42 hours probably broken sleep between children and worrying about all the things you didn’t do that day or have to do tomorrow, the mistakes you made and what a bad parent you are
8 hours settling kids/listening for them/putting them back to bed
45 hours work and commuting as you are now picking them up and dropping them at childcare
15 hours getting you and them ready and still getting nowhere
10 hours making an evening meal and feeding your child, eating yours half cold if at all
20 hours on household tasks as there is now much more mess and washing
20 hours bathing, playing, reading wishing you had more time but between work, dinner and bath time it’s almost bed time, feel like you aren’t giving enough.
4 hours baby groups and ferrying children to clubs
4 hours left to socialise, have relaxing baths, read etc and feel guilty for every second you are doing it because you feel you should be spending time with kids, cleaning the kitchen, joining the PTA and generally being a better parent.
I haven’t mentioned DH in all this as I’m going with the assumption he is doing all this with you 
And for anyone who read through all that you deserve a medal and you can tell I have teenagers because I have enough time on my hands to sort of work all that out!