The early years with kids can actually be the most rewarding and magical. You adapt to having to watch toddlers every second to make sure they don't put something gross in their mouth or run out into the street. And you learn to keep your cool and work through the fits and tantrums after a while. By the time they hit middle school, it gets pretty hard to get them to spend quality time with you as they are always wanting to be with friends instead (which is normal and healthy).
There is no perfect time to have kids. Young parents have more energy, but less patience and wisdom. The opposite is the case with older parents. It is definitely important to spend a few years married before having kids so you can get in a bunch of grownup vacations and adventures before all your vacations are to theme parks and grandparents' houses.
If you are a social butterfly, being childless and unmarried can be very fulfilling with lots of dinner parties, nights out, vacations with friends, etc. If you are not very outgoing, having kids will actually force you to make a lot more adult friends than not having kids. But there is also plenty of time in life without kids for all the adult stuff. Nothing comes close to seeing your kid take their first steps, run out of their room on Christmas morning, finally ride a bike without training wheels, and so on.