Note that from this point of view, you arrive at some measure of environmentalism. Solving climate change is much more important than random animal or plant species. But preservation of species is very important too, for reasons like ecosystem stability (we wouldn't want to stress nature too much or have a linchpin species go extinct, and make the planet less habitable in the process), drug research, food supply stability, and ultimately also aesthetic reasons.
So: climate change >> mass extinction >> occasional extinction. Microplastics I'd tentatively put between mass and occasional extinction, but proper placement depends on the outcome of further research.
Like, I get that's a biological instinct, but at some point it has to be not worth it to save ourselves. If we're making value judgments for everything else, it's simply wrong to ignore ourselves.
Frankly, microplastics issue can be dealt with later. We don't know whether and what effects they have on organisms; we're just worried about suddenly finding them everywhere. The effects might turn out to exist and be damaging, but if they were catastrophic, we'd most likely notice it by now. Mitigation efforts are warranted, but IMO should be deprioritized.
Topsoil depletion, groundwater depletion and global warming all contribute towards the same ultimate problem: less of hospitable/habitable places on the planet -> less food, water and living space -> lots of suffering and increasing economic tensions -> war -> collapse of technological civilization. Multiple problems contribute to the same bad outcome, and mitigating them should be a #1 global priority right now.
Point is: with technology - which requires a working economy - we can mitigate most inconveniences to life. We can deal with slightly broken ecosystem, and we could eventually repair it (if only as costs-saving measure). But if that economy - and I can't believe I'm saying this, that the economy is most important; but I guess this is how growing up looks like - if that economy breaks down, due to hardships of living ending up in war, we all lose. Our civilization at this point in development is extremely fragile, and advanced technology has a half-life measured in weeks. So it's most important to solve first the problems threatening our very ability to solve problems.