mac book air slow

See how apps affect Mac performance, battery runtime, temperature, and fan activity - Apple Support

Keep your Mac notebook within acceptable operating temperatures - Apple Support

A ten year old Mac is likely to have an accumulation of dust in its exhaust fan and cooling fins, causing the fan to become audible. Ideally, it should be removed by a competent repair shop.

these MacBooks especially the air is not designed for usage like the PRO models

my 2010 MacBook air runs great, streams sports and plays music but too much data use spins the fan.

the compact design make the laptop lighter and thinner meaning there is not enough ventilation like a thicker say Dell or lenovo laptop that has more space. our MacBooks feature an aluminum case unibody will gather heat and expand slightly as aluminum does. these are still great laptops, will last forever and can complete 2020 tasks, just not all at once.

i hope this hepled.

I looked at your etrecheck report; the report states that the SSD performance is poor, so it could be failing. It also states that Time Machine is not configured - my recommendation is that you make a backup as soon as possible. SSDs can fail without a warning. You are also having a lot of startup items with a minimal 4 GB RAM - the current OS runs better with a minimum of 8 GB RAM. Since there is nothing you can do about that, I’d suggest you delete all startup items; there is no need to have them all startup and run at the same time - you can launch them when needed.