The people who are seen to be the experts and authorities in social theory and practice in their ivory towers in the UN and academia cling to their outdated and falsified ideas of what works and what doesn't and refuse to change or accept new things.
Firstly, they are adamant that "tough on crime" policies do not work, they were adamant that Buekele's reforms would not work. Now sure there are probably ways they may fail and situations where they don't apply, it has now been proven by counter-example that they are wrong. They still refuse to accept it.
They now address their little El Salvador embarrassment by claiming it has caused calamitous violations of "human rights". This is a sneaky tool they use to win a debate and end the conversation, but when you look behind the curtain, really they are the ones who defined what human rights are and what is important for society, and they make no attempt to really weigh any of the multitide of very complicated issues as a whole. They just pick some human rights and some classes of people and say they were violated and that's the end of it. They would have the poor people of El Salvador live with gangs running rampant and murder rates hundreds of times higher than the rich areas of the wealthy countries they live in, and it would be worth it if only it could prevent one accused criminal having their human rights violated. It's just absolutely ludicrous, especially when you see the outcomes of these policies and they're still raging against Bukele for them and refusing to admit they don't have all the answers.
That is why they are conservative. Again, not conservative in their definitions, but conservative according to the dictionary. They hold to their views and work to maintain the status quo in terms of social and governance theories and practices.
Again I don't disagree with having strong individual rights against the justice system, and "tough on crime" policies sure can be pushed where they are not effective for political gain. But it's not black and white, it is many shades and countless inter-related moving parts. Very limited powers of police and very strong rights for accused in a justice system is a wonderful thing to have. In a society stricken by violence and crime and ruled by gangs and on the brink of collapse, it is not always possible to have without violating more rights of more people.
And if El Salvador continues long enough and keeps making progress reducing crime and breaking gangs and lifting people out of generational crime, they will actually eventually would likely to be in a much better position to implement stronger individual rights against the justice system.
What is actually important in a society is how they choose to be governed, their right to self-determination, including what rights they decide should be important and how those should be weighed and traded off among one another. Not some fixed, rigid decrees by an elitist ruling class of mostly foreigners with their lists of rights developed decades ago by and for different countries, missing many rights, and no real framework to make adjustments or make value judgements between conflicting rights, they are just used as a hammer to shut down debate that is awkward for their conservative and outdated views.