Curious about the age of your kid. Mine is 3-4 yrs old, the only one. My life has changed, a lot, over those years. What you describe was the first 18 months for me. The next year was hell with zero productivity. Then 5-day a week pre-K changed everything again. I hear it will change again in a few years even better. Hoping for it.
Mine's 2, so I'm about to hit the period that didn't work for you. I'm sure a lot varies on the specific kid's disposition. Mine's now at a stage where he loves certain activities like sorting stuff into boxes, and can spend extended periods entertaining himself with those, as long as I'm in sight.
I'm more or less mentally prepared for rapid change now though. Having seen how rapidly a child's habits can change, I know that any day can mark the beginning of a particularly hectic, or quiet, period.