They replaced the Articles of Confederation with the Constitution because they saw the Articles were a failure and the country was not going to last very long if they were not replaced.
I guess you’re going to argue that health insurance mandates or speed limits or education requirements are as bad as rule by King George III, and you’re wrong, because those actions (even if you personally don’t like them) are the acts of an elected representative government. The Founding Fathers had a very low opinion of “the peasants” and mostly wanted to make sure that they - the people with money and land - had a say in the formation of their own government. They achieved that. They espoused a lot of admirable ideas but they often fell way, way short of living up to them. In some ways we’re much closer to achieving their ideals than they were. Seriously now: if a bunch of aristocratic 18th-century slaveowners who thought women and non-property owners didn’t deserve to vote and thought Native Americans were an inconvenience wanted to tell me that the government I voted for is too tyrannical, I would have no problem telling them to fuck off.
They never would have done anything as rash as stage an armed rebellion over taxes.
That snide remark to one side, this is a question I think about on a semi-regular basis. They would be stunned by a lot of elements of our government, I think. It’s easy to conclude they would think the government has become much too large, but then again, I doubt any of them ever imagined the United States would become a technologically advanced country of 310 million people or that the national and global economies could function as they do now. There were less than 3 million citizens of the 13 colonies (not counting the slaves, of course). State and local governments still have a significant amount of power even though there government has become more federalized. They might not approve of the idea that every adult is allowed to vote regardless of race, gender, or ownership of property, but then again, consider how much more education people get now than they did 230 years ago even though idiots are not in short supply. They probably wouldn’t approve of the direct election of Senators.