Why exactly do you think anyone will be interested in following the old ways that left Tuchanka in ruins for over a thousand years?
Oh, a lot of reasons. I could point that Eve's ways are a return to the old ways that led to the apocalypse. I could mention that many of the conservatives take a perverse pride in their toughness in the adversity, or that a number of them outright state they think in terms of power and savegery as if it was a good thing. I could point to the various Krogan viewpoints of what is considered 'good' from ME1 and ME2, and how little of that is challenged or changed by Krogan characters not named Wrex or Eve. I could talk about the cultural relevance of the shamans, the rituals, the stated desires or retribution and justice for the genophage.
If I wanted to expand on the topic, with real parallels, I could point to a variety of peoples in the world whose society remains in a way that could politely be called 'medieval.' I could talk about narrow interests. I could talk about how conservatism endures.
The dissenters know they have nothing to offer the Krogan people.
The dissenters believe they are the Krogan people, and think that the Blood Rage is what give the Krogan strength.
Some of them also don't care for the collective past their clan. Since, you know, they're a tribal society.
Wrex did far more for them in 2 years than the old ways ever managed. I'm sure some males will resist the new ways and I'm sure they will fail. They might maintain a separate, significantly smaller, Krogan population in the Terminus Systems but they aren't going anywhere because, as I said, they have nothing to offer but isolation and despair. It comes down to the guy that can say I got the Genophage cured vs the guys that would still be sitting in rubble plotting their non existent revenge.
I'm not- actually, I am going to ask this. Have you ever even been to any of the 'backwards' regions of the world and asked anyone why they don't get with the program of modern civilization?
Because you sound exactly like a westerner I knew who couldn't understand why Iraqis weren't more grateful for the American invasion of Iraq and all the improvements and social progress they should have embraced.
This is ignoring that in 2/3 of the endings the Krogan by themselves will never be a major threat to the galaxy again regardless. And in the last one the threat they provide is questionable at best since they have no means of large scale space transit for the foreseeable future.
2/3?
Well, in destroy they have a buffer to build up numbers and an empire before everyone bounces into eachother. But then with Control, there's the question about whether Shepardlyst will even oppose them in the first place, or if the Krogan will be allowed to expand and grow into a form at which they are a threat. I don't think most people would advocate pre-emptive genocide (again), but the Reaper deterrant isn't permanent.
Synthesis is the most optimistic... though only if other races make themselves more like Krogan.