Human wave tactics only work well if your army consists of poorly paid conscripts with no benefits, and even then they aren't terribly effective.
One of the big takeaways I got from the Ken Burns Vietnam documentary series is that it really was a war that nobody could win. The NVA was completely outmatched and would have been crushed if the US wasn't trapped behind political barriers like the 17th parallel. At the same time the US couldn't win because the South Korean government and army was hopeless. All the US could do was "accidentally" walk into ambushes and try to kill as many North Vietnamese as possible in the hope that the government would become so weak that even the South Vietnamese army could take it.
The big takeaway is never get involved with someone else's civil war.