You say you would give more concrete examples but you go on to not give a single example and just call it "toxic". That word toxic is so overused by young people nowadays it's lost it's meaning.

Just because you are enmeshed doesn't mean that you can't function as an independent person. You won't fal over and die when you lose your partner. You will be sad, but you are still a whole person. Enmeshment doesn't automatically mean you can't function, it just means you support each other through tough shit and you are happy to do it for each other because it's a cruel world out there and having one person holding your back is nice, but not required. Enmesent doesn't mean you rely on someone else necessarily. This is what you don't get.

And you would absolutely have room if you are looking for otherature people who understand and appreciate what you want. What you forget is that favouritism is inevitable. You can't run away from it. Sometimes there is one person you love more and that's just the way it works. You can put in all the work and stuff but at the end of the day you know it's fake.

If a new partner is not okay with the enmeshment they can leave. Simple as that. You are not obligated to keep anyone happy just because you started a relationship with them. It is your choice, just like it is someone else's choice to be enmeshed.