You gotta move on through the grief, accept that they’re no longer with you, but that you gave them the best life you could. And maybe realize that giving another pet a good life doesn’t mean you’re replacing or forgetting your last one. Some people are just better at it than others, they aren’t being heartless.
That said, people who get a new dog a week or two after their previous one died are insane to me. That just feels disrespectful.
I never said anywhere that anybody needed to take on another pet. All I said was, essentially, it’s okay to do and people aren’t heartless for doing it.