Why does everyone have better units than me?

Hello. I’m wondering if I’m playing this game wrong because every time we get to the late game, I find that almost everyone has better units than me. So for the first 20 days or so, I’m moving along, taking land, building up an army, doing my researches and making sure my units (armored cars, militia, tanks, bombers, etc) are going at the same pace and the research levels are not too far behind. So around day 20, my units are levels 3-4. But for example, in this world at war round I am in, my neighbor has level 5 tactical bombers, level 6 naval bombers, level 4 armored cars, and level 5 battleships. Another player has level 6 infantry and level 5 medium tanks, along with level 5 (blueprint level) armored cars and light tanks. So how do these people get so ahead with their research? Are they using gold to speed things up a lot? I guess that’s possible, but I didn’t think that THAT many players used gold like that. Or is it that I am just doing something really wrong and am playing the wrong way? Resources are not an issue so I can research basically anything I want to. Is there a way I can play better or to use a different strategy to help me get to more and better levels of my units by the late game? If there is, if you explain it to me I would really appreciated it. Because I love playing this game but it seems that almost every round I play I get destroyed in the late game phase by a player who has more and better units than I do.