There is a pronounced tendency for male humans to be significantly larger and stronger than female humans. It's folly to pretend this tendency doesn't exist, but it's far greater folly to pretend that tendencies are a better basis for proscription than the results of actual testing. There are plenty of women who are or will be more capable than the average male infantryman, and to exclude them because most other women are not is nuts.
It's also worth pointing out that observed tendencies aren't wholly biological either. Societal expectations and opportunities are at least as significant and as society becomes more accepting of independent, athletic, women, the gender gap in ability will shrink. As long as biological differences remain, it's never going to be a 50/50 split of men and women being assigned to combat positions (barring extreme situations of total mobilization, or where attrition has dramatically reduced the number of males of combat age), probably won't even be close, but the gap will narrow in the mid to long-term, even if women are held to the same standards.
This is changing. Barring some radical intervention, the ACFT and OPAT are only weeks away from being implemented and are intended to be age and gender-neutral. The requirements are based on MOS, so those not likely to be in physically demanding positions will have an easier time than before, while some of those in more demanding assignments (combat infantry related, for example) will be harder to pass than prior tests. This will probably limit the number of women in direct combat roles, at least until society and training catch up...but those that get through will have been tested to the same standards as their male peers.
Mostly because people have a tendency to be fatter and it's getting harder to find recruits that can meet requirements in the quantities desired. That tendency doesn't mean that everyone is fat.
As for the lowering of standards...where those standard were implemented with good reason, I entirely agree, lowering them is not ideal. However, until society starts producing healthier people, it may be necessary.