The IRA's goal was the unification of Ireland through violence and they've not succeeded
Yes, the provisional IRA wanted the unification of Ulster with the Republic or Ireland. However, the latter is the direct descendant of the Irish Free State, which only existed because of the "old" IRA's activities.
The IRA got themselves into a situation where they were riddled with informers and finally, under a Labour government, agreed to a peace deal whereby they agreed with the UK's position that the future of Northern Ireland would be settled democratically.
In the Good Friday Agreement, which required them to disarm and disband, it was agreed that there would be an end to direct rule from Westminster, powers would be devolved to Stormont, cross-community majority agreement on certain major decisions would be required and a border poll must be called promptly if it looked likely that a majority in NI would vote for unification with the Republic. Neither Wales nor Scotland have the right for a border poll if their nationalists have reason to believe they have the votes to win it.
Those organisations were fighting against regimes that were unjust. Those "Terrorist/Freedom Fighter" organisations didn't win anything through violence.
The Salisbury Agreement (which ended the Southern Rhodesian civil war) called for the creation of an interim government in which black Southern Rhodesians were included in leading government positions for the first time, while an independent civil service, judiciary, police force and army were created. It required a new constitution to be drawn up where black Southern Rhodesians would have equal rights, followed by the holding of an overseen* General Election in which whites and blacks could vote. Seems like a win for violence then.
*The subsequent General Election was overseen by agents of the British government.
As you have said, the "Status Quo" will remain while the "establishment" is unchanged, and the Establishment is not going to change while the majority of people want the status quo to remain. ...
They may be ahead of their time, and World opinion will change to support them, but I don't think it will be in my lifetime. There's too much money invested.
Yes, the establishment cares far more about money than the environmental consequences of pollution.
Fossil fuel companies make trillions of dollars in profits* every year and have trillions more invested in the infrastructure of oil, gas and coal. They have also received trillions of dollars of subsidies from governments around the world. They will never give all that up without a big fight. They have dozens of PR agencies, lawyers and corrupt politicians on speed dial to stem any attempt to slow or stop them. They can whistle up a small army of influential lobbyists with a few phone calls.
The result of this is watered-down global climate agreements that few countries bother to obey. Add to that 14 years of cynical Tories here, 4 years (and maybe 4 more to come) of Trump's environmental vandalism in the US, powerful (fossil fuel funded) climate change denying groups with tentacles everywhere and, most importantly, a western world with a majority of selfish entitled people who have no desire or inclination to confront the realities of the climate crisis.
We're on course for a 3 degrees centigrade increase over the pre-industrial mean global temperature by 2100. It's going to be a global disaster. It's going to kill millions and displace hundreds of millions of people (from previously fertile land) in this century. People have gone to war over far smaller problems.
*
Global fossil fuel industry profits were approximately $4 trillion in 2022