My experience with this has come from Worldbuilding Pasta, and I can’t seem to find an answer online.
A mid-ocean ridge can be subducted, because subduction is often faster than the rifting of the ridge. As soon as the ridge is fully subducted, the oceanic plate can no longer grow at all and will eventually be fully subducted. Then your continents collide.
Spreading centers that get subducted can do a number of different things. The spreading center getting subducted can cause the boundary to switch from subduction to being a transform fault. The Farallon Plate poked under NA and switched, eventually attaching a piece of NA to the Pacific Plate and rifting behind it, scooting the edge of Mexico up to become the Baja California Peninsula. The remnants of the Farallon Plate still exist and are being actively subducted to the north and south of this fault area (San Andreas)
The spreading centers can also get subducted and then each side of the rift can kinda drift apart under the subduction zone like two separate napkins gliding away (a slab window) and this can cause the volcanism to stop or the slabs themselves to get stuck and sorta ride along under the overriding plate (Flat Slab), which also tends to stop active subduction volcanism. (Look up papers on the subduction of the Nazca Ridge and the Chile Triple Junction. They explain it better.)
I think that it’s important to keep in mind that the subduction zone itself is not a static thing. I feel the worldbuilding guides seem to imagine the overriding plate as this big super hard block, but the edge of the zone can bow back, tear off pieces, “gloop” over the top really fast and stretch everything else out behind it, etc. The flat slab subduction is particularly good at this, because the overriding plate has orogeny way deeper inside than the arc volcanism at the edge and often it stretches out and makes stuff like the Basin and Range Province in the USA.
I would honestly suggest trying to look up research papers of tectonic development in specific areas. You learn so much by just reading about a specific cluster of features or a specific place.
