Yes to all that you’ve said! Sex is more than just the mechanics and no man has ever been truly unhappy with a vagina, in part because they are elastic. Someone with a background in biology ought to know that.
Estrogen fluctuations as part of your monthly cycle or as a part of aging may contribute to slight changes in the relative looseness of your vagina, but even this is typically barely noticeable in most people. Aging and in some cases, having children, are the main things that can cause a vagina to become slightly looser. Pelvic tilts, Kegels, and hormone replacement are available to those who need a bit of a boost.
The bottom line is that sex is healthy and natural for women (and for everyone). No amount of sexual penetration is going to change the characteristics of your vaginal tightness, and anyone acting like it will is just telling an outdated myth designed to shame and control women.
