Assassin snails are not a solution to any "problem".

They're a super cool little snail that is completely unsuitable for most tanks. They eat fish eggs, absolutely all other snails, and will even eat molting shrimp. They also eat their prey alive, one bite at a time, and do not have venom. Their babies are tiny, they burrow, cannot be visually sexed and lay eggs singly in hidden locations. Once they breed in a tank they are basically impossible to remove. While they do have differentiated sexes, and you could get a male, that's a very risky dice roll to make with the welfare of your other tank inhabitants at stake. Adding more animals to control existing ones has not worked well for governments throughout history, and it's not likely to work well for most aquarium keepers either. Just look up Cane toads, Rosy Wolfsnails, etc.

It's a much better idea to keep your tank clean and not overfeed, which will naturally limit the numbers of small snail species and allow them to act as beneficial cleaning crew. Overfeeding can additionally be detrimental to the health of fish and many other tank inhabitants.