The thing to understand is that the EU has changed a lot over time. You're right to observe that the UK had many opt outs of various forms, but this comes with two extremely severe caveats:
1. They were all old. When the EU was smaller and the Commission less powerful, it was more willing to compromise. As it grew and took over more powers, its appetite for compromise lessened. It started to talk about competing approaches or partial cooperation derisively ("cherry picking") and refused to contemplate looser integrations.
2. They were getting unreliable. The UK secured an opt-out when the vague collection of principles called "human rights" was translated nearly directly into law - a bad move, constitutionally, and one the UK was wise to reject. The human rights were never written to be laws and could not function properly as such, so the UK insisted on an opt-out and got it along with Poland. The relevant bit of law is as clear as can be: UK and Poland are not subject to those laws. But as often the case with the EU the written word turned out to be utterly worthless. The ECJ simply ruled later that the opt-out was void. No actual real legal justification was provided - they just annulled it by fiat, and told the UK its opt-out was gone. And because EU membership means obeying the ECJ in all matters, that was that. No more opt out.
Now comes Brexit. Enormous numbers of proposals were tried by the UK to stay with closer alignment, a free trade deal, continuing in the Horizon research programme etc. All were rejected by the EU and we ended up with a relatively "hard" Brexit.
I did vote for Brexit and still support it strongly, partly because of things like this. The EU of 1992 is not the EU of 2022. It knows many populations don't want the level of control the EU currently has, and it feels like if it gives up even an inch the whole anti-democratic project will start to fall apart. Indeed one of the primary motivations of the EU negotiators during the Brexit talks was to not do anything that might encourage other countries to re-assert independence in any area, even if they didn't want to leave.
1. They were all old. When the EU was smaller and the Commission less powerful, it was more willing to compromise. As it grew and took over more powers, its appetite for compromise lessened. It started to talk about competing approaches or partial cooperation derisively ("cherry picking") and refused to contemplate looser integrations.
2. They were getting unreliable. The UK secured an opt-out when the vague collection of principles called "human rights" was translated nearly directly into law - a bad move, constitutionally, and one the UK was wise to reject. The human rights were never written to be laws and could not function properly as such, so the UK insisted on an opt-out and got it along with Poland. The relevant bit of law is as clear as can be: UK and Poland are not subject to those laws. But as often the case with the EU the written word turned out to be utterly worthless. The ECJ simply ruled later that the opt-out was void. No actual real legal justification was provided - they just annulled it by fiat, and told the UK its opt-out was gone. And because EU membership means obeying the ECJ in all matters, that was that. No more opt out.
Now comes Brexit. Enormous numbers of proposals were tried by the UK to stay with closer alignment, a free trade deal, continuing in the Horizon research programme etc. All were rejected by the EU and we ended up with a relatively "hard" Brexit.
I did vote for Brexit and still support it strongly, partly because of things like this. The EU of 1992 is not the EU of 2022. It knows many populations don't want the level of control the EU currently has, and it feels like if it gives up even an inch the whole anti-democratic project will start to fall apart. Indeed one of the primary motivations of the EU negotiators during the Brexit talks was to not do anything that might encourage other countries to re-assert independence in any area, even if they didn't want to leave.