*Of course there's huge responsibility to raising kids, but it's as if someone who is single must somehow have extra love/commitment/superpowers to "take one" their partner's kids.
I've know plenty of people who LOVE the kids of their partner. They don't take them on as if it's some kind of endurance test, but actually feel lucky & happy to have the additional joy of children as part of their new relationship.*
I became a stepmum to 3, then became mum to 3 as well. I absolutely did have to have extra love / commitment/superpowers when I took on my husband's kids - it's really hard to be a stepmum! Especially when you're in your early 30s, and have never had kids yourself and have no idea what you're doing.
All the stuff that oils the wheels of difficult times with your own kids (the fact that they are yours, the fact that you can make parenting decisions) isn't there when you're encountering difficult stuff with your step kids. *
*
I had to dig really deep and find more patience, more forbearance, more compassion that I could ever have imagined, certainly more than in previous relationships with guys who didn't have kids. It absolutely can feel like an endurance test at times!
It was completely worth it - I really love my stepkids (who are, thankfully, delightful people), I have put a hell of a lot of effort into developing a lovely rewarding relationship with each of them and I do feel lucky to have them.
AND ALSO - any fool can blithely date someone with kids and shrug and say 'Yeah no biggie', but if you have any kind of sense of responsibility or pragmatism or understanding what a powerful impact stepparents can have on children's lives, it's a big commitment to take on.
Perhaps, OP, you might benefit from talking to some step-parents of 3 or 4 kids in real life, to help build some empathy.