This is kind of a Yes and a no answer so bare with me.
As far as heating issue impacting performance this is absolutely a viable reason for poor performance. When a piece of hardware begins to run "too hot" then they will begin to pull back their performance in order to reduce heat and in turn save themselves. This is a situation called "thermal throttling" and is a very common issue in laptops and tight computers, as well as older computers that are filled with dust.
The question as to whether or not this will return the PC to previous performance is not so cut and dry. If you are monitoring your temps and you are noticing abnormally high temperatures then yes dusting your pc will very likely improve performance to some degree. This will not necessarily make the pc "feel like new again". If the system is very old, if the storage is getting cluttered, or if the quality of games you are playing continuing to increase while the pc remains stagnant, then this will not wholly fix the issues.
But yes if you believe you are thermal throttling then a good cleaning can absolutely improve performance. Make sure you reach the problem areas especially. Dust out the aluminium fins on your CPU heatsink (if air cooling, check the radiator if water cooling) and the aluminium fins hidden underneath the shroud of your graphics card. Try to hold the fans in place while you hit these areas with air you ensure you don't break the bearings. Also if your pc is particularly old (I'd say over 4 years) maybe consider replacing the thermal compound on the CPU for better heat transfer
Good Luck!