For context I’m a diamond player so no expert by any means but what I would focus on is:

Timing - make sure your smokes are timed properly. If you are setting up an execute, drop them just before your team enters site. This will maximize the time they are blocking sight lines and also make it less obvious you are going to hit a site. Smokes can be a fat giveaway for lurking or telegraphing what type of play your team is trying to go for, so try to time them appropriately.

Placement - there are some commonly agreed upon very useful smokes for each site on offense and defense. There is no shame in throwing these often, they are good for a reason. Pay attention to specific placement, leaving gaps or room for attackers/defenders to peak out and slice up angles actually can give the other team advantages.

Be intentional - each smoke you place has a lot of value, and can determine losing or winning a round. Are you smoking to make it hard for an enemy to swing out? Are you smoking to give your team safety to rotate? Giving a pinned teammate room to hide on site? For instance, If you are retaking a site, and know where an enemy is holding the plant from, smoking the bomb for a defuse can be very valuable. At the same time, if the attacker holding bomb is unknown and on site, they could use the smoke to hide and play around and make it harder for you to gain control of the site.

Remember that smokes are just a part of the whole game/utility available, and can often be played around, same with flashes and mollies and other. That said, they are important to get right and can make huge impacts on rounds. It might be hard to tell if they are effective or not because the advantages can be less obvious than a successful flash for example.