One common misperception is that this would be a "Constitutional Convention", meaning that the whole of the Constitution would be up for possible revision. That is incorrect. This would be an Article 5 convention. Article 5 only allows the calling of the convention to propose amendments to the Constitution, not to rewrite the Constitution. And any amendments proposed by the convention would still have to go through the normal ratification process, meaning 38 states would have to ratify any amendments proposed. Can you imagine 38 states ratifying amendments abolishing the 1st and 2nd amendments?
You are partly correct. Any amendments passed would still need to be ratified by 3/4 of the states. So there is that safeguard. But there really is no limit on what the convention can propose. Which is to say that yes, the entire Constitution is theoretically open to revision.
And again, too many people are assuming this will be a conservative convention. Given how evenly divided the country is, that is a very unrealistic assumption. A convention is potentially dangerous.