Plantera is quite easy, but people make it hard by going through the trouble of making a huge arena. Get fetid bagnakhs from the crimson mimic, get some melee damage boosters and BAM.
I'm post moonlord on my switch, on tmodloader I am pre-mech boss.
I dont have a crimson world but you can easily cheese it by making/finding a big enough area and just use your wings to fly circles around it while spamming a weapon that has enough range so that you can hit it but it cant hit you, btw i am post moonlord pc and have a legendary zenith and have killed daytime empress of light