I don't mean to brag, but never since I first attained Profeshional status have I ranked down (I have been close 2 or 3 times). I usually always make it to the third wave, but I'm almost never the one in my team with the most golden or orange eggs. In fact a lot of times I'm the one with the fewer golden eggs. What I mean is that if you're deranking often, try changing your strategy. Watch your team, if they're eager to go after golden eggs you can prioritize other things, if they focus on killing Salmonids focus on retrieving the eggs yourself. And always try to provide support as well as to know when you can't do things in your own. Like going through 3 chums to reach a Flyfish means you won't have ink to throw a bomb, so maybe fall back and call a teammate for help instead of pushing through and getting cornered by a Steel Eel that appeared from out of nowhere.
In Turf War I tend to go my own way, but I've found that SR relies on teamwork much more. I'm never the MVP in SR but I'm not having the same experience of shitty teammates a lot of you talk about here (for the most part), so either I'm extremely lucky with my teams or I'm doing something well. I think my main point is that if you're failing often in SR try to play a support role, it seems to be working fine for me.
Again I'm not trying to brag, just to help, if anything I wrote seems the other way please understand that english is not my mother language.