I think people have issue with the phrase your husband used….
If he said, “I’m so glad we still have a great relationship and sex life after the baby,”that would be one thing.
But, he said, “Thank you for making sure we didn’t lose us,” which puts all the onus on you being the good little woman and dressing up in saucy gear, and zero onus on him putting in any effort whatsoever. It also frames sex as being the main basis upon which your relationship is built; while a healthy sex life is important, it shouldn’t be the absolute fundamental aspect.
It’s also problematic that you are giving the exemplar of dressing up in lingerie as an example of being a good wife/female in a relationship…. It really isn’t necessary, if that is what works for you and your relationship, great, but don’t impose this upon other people because it isn’t a prerequisite or important in the majority of relationships. Furthermore, personally I think women should get dressed up for themselves if they wish, but to dress up for a male partner is a bit 1950s.
Finally, by gloating in the manner you have, you’ve disregarded the very many women who may have post birth issues entirely out of their control such as - vaginal tear, caesarean recovery, PND etc that may get in the way of sex. And the very many couples who may have issues after having a baby such as disabled/ND baby, money issues, change in other family dynamics and so forth.
OP, you are very, very early days with only one child. When you have successfully reared 2-3 to adulthood without any impediment on your relationship, then you come back and tell us all how you did it. To assume that your relationship will continue to go on unchanged without growth is naive.
Please don’t try to castigate other women or bring them down for expressing how they feel when problems arise early on. If you have had plain sailing so far great, but there will be challenges at some point so don’t take it for granted that you will always have time or energy to continue performing for your husband as you have been.