For example, if you sell something before you have paid for it (this is very common), and then put the money from selling into a bank where it earns interest, and then withdraw that money and pay for the thing you sold:
You will have made sale_price - purchase_price + interest.
In a VAT system, you will pay VAT on sale_price - purchase_price (or your customer will, depending on how you sell things), but not on the extra interest you earned.
So that's already a loophole. You can game the tax system by selling things before you buy them and earning interest.
If you're smart enough, you might even sell things for exactly the same as you pay for them, and still make a profit due to the interest while you hold the money. You could get even smarter, and hold that money on behalf of your upstream supplier to withdraw when they need to spend it. Before you know it, you're paying zero VAT, and all your profit looks like interest.
But you have to pay an accountant to make sense of all these for you. The cost of the accountant isn't a direct cost of making the thing you're selling.
So that gives you the difference between gross profit (sales price minus costs associated with the thing you're selling) and net profit (what you have after paying for everything needed to run the business).
That's literally a tax on value added.
With a broad enough definition and inclusion of other, unrelated prices at that negative part, one can claim that in a time-frame of several years, both average to nearly the same. But that doesn't make them equal, and if you go read those tax-codes, you will discover the ones being discussed add to very different figures even on the long term.
I'll just add here another encouragement to go out and get an understanding of tax codes. Odds are they will be relevant for everybody that frequents here at some point on their lives, and odds are that if you don't know them, you'll only discover their relevance after the fact, when they have already caused you some problem.