NoOneCares, I understand where you're coming from. I was also 1500 ladder before and thought certainly strategies were unbeatable. However, I got eventually managed to get better and realized that that simply wasn't the case, that I had made a lot of mistakes in my games and if I had played better I would, well, have not necessarily won the game but moved onto the next stage of the game.
You can think of the game as a series of skill checks—in this specific case, your opponent might be doing a T1 land strategy. You have to pass this test. There is probably a range for the "correct" amount of t1 land factories you must make on a given map in order to pass this test, and I suspect that number is generally higher than you think, so you keep failing this test. You can make less land factories than your opponent and use defender's advantage + good micro to get an advantage elsewhere, whether it's T2 mex, T2 land, etc. and move onto the next stage of the game. You also get diminishing returns for each T1 land factory you add on so it's pretty much never the "optimal" strategy to go full T1 spam between two sufficiently evenly skilled players on basically every one of the maps you listed as a land spam map that isn't a 5x5.