You're old enough to know better than this. Will a wall 100% stop illegals? No. Will it deter and slow them? Yes. Not rocket science here.
You are correct. Something is better than nothing which isn't saying much in this case. Most experts agree the border walls work best when there is sufficient manpower to patrol them. Manpower is expensive as is the cost of building and maintaining additional border walls. Many folks, including our Representatives in the House strongly oppose increases in spending. Therein lies the conundrum. Something and someone must compromise if they are to reach an agreement.
Do you personally know people or anyone who works as a border patrol agent? If so, it behooves you to have a conversation with them about what does and does not work. By most estimates, the U.S. border patrol needs somewhere around 22,000 - 23,000 employees to be effective. Senior border patrol agents with overtime average annual salary are nearly $150,000.
My cousin is a career border patrol agent who has mostly worked at the southern border, but also at the border between the U.S. and Canada. He is a senior agent specializing in the Horse Patrol Unit (HPU).
This article is outdated, but the principles therein still apply. A wall can only do so much.
https://www.theatlantic.com/ideas/archive/2019/01/trump-nbpc/580237/ https://www.cbp.gov/careers/ofo/pay-benefits/cbpo