According to statistics, beginners hardly throw grenades and mid-rank players throw a lot of grenades, but they often do so thoughtlessly. Professionals also use a lot of grenades, but they do it most effectively.
Each grenade can do more good than any other firearm. The right smoke covering the right choke point or pass gives time to pick up on the enemy or to stop the fastest rush.
There are many guides available for each map and each position. Learn how to spread out grenades on the maps and it will have a positive effect on your playing skills in CSGO.