Mobs spawn too much in easy mode (sometimes normal and hard too)

I was playing Minecraft trying to speed run but I noticed that in mines and caves, hostile mobs spawn way too much especially creepers. when I go into a cave, I always come across an endless cycle of creepers coming out. I would kill one than another comes, kill that and another comes which continues for like 5 minutes until I can actually venture into the cave. No there is no spawner, every time I come across this problem I would check if there is a spawner. I remember I found a skeleton spawner so I knew that a lot of skeletons would spawn which happened and made sense. I had a shield so I could deflect all the arrows and just kill them one at a time which would be pretty easy however when I dropped down to the spawner I noticed that in another cave right next to me there was almost a hundred mobs coming towards me. I continued to fight the skeletons so I don't have to deal with the arrows so I can deflect creeper explosions but I didn't have enough time and died by a creeper explosion. I am very good at speed running (not the best tho) and I want to get as good as Dream (Youtuber) but I can't practice speed running with this problem because I can't find diamonds without not seeing a billion creepers and other hostile mobs coming after me.