The Saiyan society make so little sense it hurts. There's no way that a society of warriors, every member of which gets several times stronger each time they come close to death, and with access to healing pods capable of healing even the most grievous of injuries in a matter of days, hasn't produced anyone capable of even rivaling Frieza's 1st form.
It literally doesn't make sense. At all.
Well, the two things to consider are that, 1) Saiyans are kinda' stupid, from everything we've seen (though hybrids do alright), and probably didn't think it through if they ever even realized it was happening to begin with, and 2) There's not actually much showing the strength-on-near-death thing is particularly notable. Most of the Z saiyans have this thing were they didn't actually get close to death, they outright died, usually repeatedly. And beyond that, most of the notable ones were, well, odd, iirc. Royal bloodlines and junk.
1) Vegeta knew about this ability. There's no reason to believe that he was the only one with that knowledge.
2) Again, Vegeta has exploited this ability of getting powered up after near death in Namek saga
extensively. He got from 18,000 to somewhere close to Frieza's 1st form (~500,000) in just, what, 3 near-death experiences? 1st on Earth, 2nd to Zarbon, 3rd to Recoome. Though the first two power-ups were kind of shitty percentage-wise, the third one really blew his power level up. Oh and then there's the
4th near-death experience from Krillin, which upped his power level high enough to be able to achieve Super Saiyan after one-two years of training.
And while Vegeta was of royal blood, elite-class warrior and all that, Goku, on the other hand, was a "low-class trash", and his power level has risen immensely after the gravity chamber training, with multiple-near death experiences.
Maybe Frieza was prudent enought to kill off, in one way or another, any Saiyan that became too strong for his tastes.
He did send assassins to kill Bardock and his crew in the movie. And apparently Akira Toriyama directed that one, so probably canonical.
And Bardock was surprised as hell when that happened, indicating that it was highly unusual.
Also, Namekians can apparently fuse and divide themselves into other beings at will, so why didn't they just fuse themselves into a huge badass namekian and kick frieza out of reality? After that, they could've just divided themselves back into a species again.
They could've become the god emperor of namekind or something.
That was probably an ability reserved for a warrior-caste Namekians. And Nail was the only warrior-caste Namekian on Namek. Dende was a healer-caste, that elder looking guy was an elder-caste (the one that can produce Dragon Balls, when aged properly), and others were probably some farmer-caste shit-tier Namekians.
The bigger question here is how the fuck a simple drought managed to nearly wipe out an entire civilization of beings capable of producing fucking Dragon Balls to make fucking wishes. It makes just as much sense as a meteor wiping out a planet filled with planet-busters.