As someone who falls ( no pun intended ) into this category, there is a lot of sense in this article . However , joint damage over many years abusing one’s body , can cause issues with the indicated exercises . Thai chi is a good solution .
Cycling outdoors is a good way of maintaining lower body strength ( not necessarily total off road - gravel / track riding ) does help whilst keeping the loads on lower joints acceptable ( relatively pain free ) .
That’s my two penny worth ,