There’s no luck to it at all.
You replace the struts, and the problem will go away.
You will then have a 91 Camry that rides so much better than it has for the past 20k miles.
How long do you plan on keeping this car?
If you want it to last, and you like it, who cares what the KBB or NADA valuation is?
If you bought it for $500, and can’t afford to replace them, then that’s a different story.
My co-worker sitting next to me has a '94 Camry, with 264k miles on it, and his rear struts are bad too, and perform exactly the same way you described. My gf’s daughter has a '92 Camry with 172k, and they are not as bad yet as your car, and his car, but they compress easily, and it bottoms out going over large bumps, like our driveway curb.
Her car has way more problems than the struts right now, and isn’t worth sinking the money into, at this time. Her father bought the car for way too much money (~$2500, idiot), with visible front end damage on it (damaged hood, no grill, headlights held with bailing wire, hood held down with bungee cords originally, etc), bald tires, and its been a money pit so far.
Luckily she inherited a slightly better '98 Corolla from her recently passed away aunt, with 173k miles on it, that is physically in much better shape, but it has low compression in one cylinder, and has a vanishing oil issue that I haven’t been able to look at long enough to determine if its from the low compression cylinder, or from an external leak.
It needs new struts, too.
Low man on the totem pole, at this point in time.
But, if the rest of the car checks out, then the struts will eventually get replaced, by me, in my garage at home. Just like I did on my '98 Porsche Boxster, within a month of purchasing it. It only had 80k miles on it at the time, but the right rear was blown, and was leaking oil. It had completely different symptoms than what you’ve described, however.
BC.