“If they were meant to be The One then they would still be participating in life with you.” How true is that statement?

I’m not a big fan of ‘the one’ type thinking. I’ve seen it cause more harm than good. I’ve seen way too many people latched onto the idea, so they stay in toxic relationships until it nearly destroys them OR it becomes the belief that prevents them from processing their grief / being able to continue living their life in a healthy, receptive way.
Aside from moments of being sweet together, I have never once seen someone in a happy, healthy relationship have to hyper-focus on them being ‘the one’ — because they don’t need to. The quality of the relationship/friendship speaks for itself.

I disagree with this.

Nah- no such thing as The One

I don't believe that there is necessarily just The One, and that over time, one meets several people who can fit those criteria.