I’ve only ever had serious longterm live-in relationships and this never happened with me. Did I ever feel lonely, like I was the only one really in a “relationship” and the other person was just cruising along to see what would happen, if they wanted to invest in the same way I had? Yeah and it sucked but so at one point I asked them to step up or let me go and the relationship took a turn for the worse and then for the better.
My observation is people are going to do what they’re going to do. You can light a fire under them and push them to reveal what they think or feel in less eloquent ways than they’d initially choose but don’t assume that change things to your favor.