In every Magic game, there are some spells that stay on the battlefield (permanents), and others that create a fleeting effect and then go away. Generally, permanents generate bigger advantages the longer they stay in play, so in competitive play it’s very common for both players to destroy their opponents’ permanents almost as quickly as they appear.
There are also ways to have answers for the spells that are not permanent. Of course, if you fill your deck with too many answers, you won’t have enough ways to actually win, this may not be a huge problem as long as you can keep answering things that come your way.
Every answer is conditional: it will stop some cards but not others (this is less true in Modern and Legacy). So, once you know the details of the most common decks in the meta-game, you can sculpt your package of removal and answers around the permanents and threats you find there.
You can also design your win conditions to dodge the removal and answers that those top decks are liable to have. For instance, Shock and Fatal Push are very common removal spells. If you don’t have any creatures that cost 2 or less, or have toughness 2 or less, you can partially “turn off” those spells, and since a player often just has 3 or 4 cards in their hand, having one or two dead spells is a big disadvantage. It may not be ideal to exclude all the creatures that die to those spells, but it is something to consider since your deck will face removal over and over.
This video gives a cool example of a deck that's way off the beaten path but still knows how its answers should work. It has a lot of effects that move cards and lands between the various zones - and even pulls cards out of the opponent’s deck preemptively.