High Ping and Packet Loss in Gaming

In games such as CSGO, Rainbow Six Siege, Fortnite, and PUBG, I have really high ping and packetloss. Sometimes the ping is great and the packet loss is bad, but other times the ping is horrible and so is packet loss. Sometimes my ping ranges from 10ms - 70ms. Othertimes it ranges from 60ms - 300ms. Packetloss sometimes ranges from 0% - 10%, but other times it ranges from 10% - 100%. Sometimes I can't even watch videos in 720p. I contacted the ISP once and they sent a technician out, but he said that nothing could be fixed. They swapped out for another modem and nothing. He said it can't be fixed, however I don't believe that because we shouldn't be having poor internet like this.