You're not a rubbish parent OP :) 
I was signed off work at only 26 weeks pregnant a couple of weeks ago and have a 2 year old DD at home, and she has definitely been spending more time entertaining herself than she does if I'm usually at home, and this is absolutely fine. I've always been a fan of "lazy parenting" and self direct learning/play anyway. It started when PFB DD was around 6 months old, and I spent her whole 2 hour nap preparing a carefully curated, very beautiful looking activity. She woke up, wasnt interested at all and just wanted me to sing songs with hand actions while I sat her up in my lap.
It made me realise as she's got older and there is more and more pressure to be doing this and that, that its just not nexessary - when I know and see in her behaviour that she just needs to know me and her father are here for her, and take care of her, and respond to her.
Now that she is 2, I'm so glad I don't put huge pressure on myself to make sure every day is the kind of day you would hear about on social media or something and feel inadequate about. My DD loves our days together, and routine and repeated activities are good for their development. Doing something completely different and out of the way every day is not even beneficial for them and puts so much stress on the parent.
It's a bit silly but since being pregnant again I've been thinking about out ancestors, how their lives would have been centered around the same places and activities, and about how important it wold have been to care for your child bit also to raise them to be independent. I simply cant believe that we would have survived as a species if the essential needs of our children revolved around being entertained by the parent 24/7 - surely gentle guidance from the parent with independent interaction with the world they are coming to know is much better for them?
And I feel that the best thing you can do for their social and emotional development is to be responsive in a positive way - much easier of you are not breaking your back to organise a load of activities that they may not even want to engage in, and allow your self your own down time. I have properly waffled on here, I'm typing one handed while me and DD play piano and I can't even remember what I've written 