The US Constitution has been watered down by the SCOTUS over the last one hundred years. They have found in favor of using the Interstate Commerce Clause to expand the size and scope of the federal government.
When doing this the federal government takes away rights and powers left to the states under the 10th Amendment.
The 16th amendment was also passed by them as constitutional even though it circumvented apportionment for income taxes. The power to tax was already in the constitution but this amendment took away the apportionment between the states.
The 14th amendment didn't give Black men the right to vote, nor did it give Women the right to vote. These were given by the 15th, and 19th amendment. The latter was 55 years after the 15th.
The constitution is silent about the validity of the simple majority vote of the SCOTUS. The constitution was also silent on the details of creating the SCOTUS, because the founders left it up to Congress to setup.
Same sex marriages should have required an amendment, as the SCOTUS didn't give any real reason why it should be forced upon the states. These were states rights that were trampled by the SCOTUS.
As I mentioned, the 14th amendment didn't even operate with clarity, and equality for the right to vote, which is an inherent right in a democratic republic.
The structure of the three branches of government needs to be changed as it has clearly failed us this century. We need these amendments to catch up with technology, and all the changes it has created for elections, campaigning, etc.
The continuing gridlock of congress, and the de facto legislative actions by the president need to be addressed by amendment.
The political system has failed due to the divergent goals of the two political parties, and I doubt the founders anticipated this when they created the constitution. Having the 3 branches of govt seemed like a good check and balance, but it didn't really work this century.
I could go on but I am running out of characters for comments here.
Short answer, the Constitution is leaking, and it needs amendments to stop those leaks.