A lot of people are saying "Get rid of lag" well they can't really help and you yourself. It really depends on what computer you have, ram etc. Like famous Youtubers, they don't worry about lag. Also the game minecraft is very laggy. They can't help it. All the blocks being put in chunks then loaded it just becomes a lag city.
Also what I'd like to have in Minecraft is probably a lot more weapons more building blocks. Much more, the list will go on for ages xD