While it's definitely a bummer to end a relationship you were enjoying, I'm glad you were able to voice your boundary around sex!
It's true that sex is an important part of of relationships for some people, but that doesn't mean everyone you date will decide to end the relationship because you're not ready to be sexual (heck, they might not be ready either, or you might feel ready before they do). Too, depending on your comfort level and theirs there are lots of sexual activities besides intercourse that you both could be interested and comfortable trying. So, while your boundary around sex may eliminate some potential partners, there will still be plenty out there who are happy waiting until you're both comfortable. Does that help?
(Too, right now you'll have even more time before reaching those conversations, as the pandemic means it'll take longer for sex with a new person to even be a safe thing to pursue.)