You will discover more small things, as you get better. For example, if you have better micro on your t1 bombers, you can get more damage from them. (And I don't just mean split attack, I mean getting them to slow down so you can get faster attacks on enemy engineers, and try to avoid making big looping passes every time they drop a bomb). There are many, many ways you can micro units to try to get an advantage. Manual reclaim is just one of a thousand things competing for your attention. You can try to hide tanks behind factories to soak damage for them, get LABs into range of engineers to shoot them but move out of range of being reclaimed, try to dodge tank shots while your LAB is killing the tank, if you're trying to shoot down a transport, you might want your interceptors to not "overshoot" it (fly past it), etc. etc.
Also, you should only get matched to people with much higher rating during approximately your first 5-10 ladder matches. Once the system has confidence in your ladder rating, it will try to pair you up only with people near your rating. So you shouldn't run into 800s any more on the ladder unless of course you get your rating up by winning a lot.
Where manual reclaim has the most impact is (1) as part of a starting build, which is also when you have a lot more spare APM because you only have like 1 factory and 3 units to micro, and (2) when there is a single big piece of reclaim, like a strat bomber dies and leaves 1300 mass on the ground and you don't want your engineers getting distracted by small stuff around it. You can practice build orders (which is something that everyone who wants to play competitively needs to do) and the other situation doesn't happen enough to be a problem.
You can also learn how to use "factory attack-move." An engineer on FAM will scoop more quickly than an engineer on regular attack-move or on a regular patrol order. It moves around less, scoops at further distance, so it has less time wasted between scoops. It's kind of a silly thing, but good players will use it to reclaim things more efficiently and it doesn't cost much APM.