Hey there, you need response, remember that you never play alone and in modern your opponent may make you want to burn your own deck after the match, if you want to go full mono green, you should play some staples to control,
accelerate or ramp, green is good with ramp, if you use ramp, exploit it, use big badass creatures, or game-changing spells, I don't want to tell you what to play, since I don't play green too much, but if you encounter a blue player, how are you going to play if every creature you cast is countered? If you are playing against a black player, how are you going to keep your creatures from being destroyed? If you play against a quick deck (like burn for example), how are you going to stay
alive long enough to play your own threats? Good luck and welcome to the modern format, where every new set forces you to adapt to new threats