Never had a problem with entry/exit. My wife has knee issues and she has no difficulties; of greater concern were the urchins which could put a hurting on one should one put a foot wrong.....
The urchins are there, but usually not too bad, UNLESS you shore diver the eastern, or Wild side. THERE the urchins carpet the shallows, which are swept by much stronger surge continually, than the western more sheltered side where almost all the diving is done. The wild side you really need a guide or a boat dive.
I have a bad leg, and my gf has some back problems. If I have any question about the entry at a dive site, I do it first in just my dive boots, hard sole, and get a good feel for the entry, before I gear up.
Then I help Colleen into the water til she is @ waist deep, where she can stop, put on her fins, and drift. I have carried her tank out for her, when the surge was a problem. I then return to shore, gear up and do my entry.
As Bubbletrubble said, there are quite often piles of rocks that have been left by previous divers, to mark the better entry and exit points. As you enter, turn back and do an under water survey of the entry point, so you can return to that exact point for the exit.
Staying low, keeping your fins in your hands, and making sure of your footing before the next step is a big help.
To me boat diving is no guarantee of easy, pain free exits. My worst tumble was when an unexpected large wave lifted the stern clear of the ocean, and tried to sweep me off the ladder, and split open my leg (not sure what part of the Caribbean we were on the trip).
No entry I have ever done on Bonaire, even the few I that did take a tumble during, compare with the N Atlantic washing machine entries we did as teens on the MA and ME coastline. THOSE were rough, surf and rock entries that required serious timing and luck.