YNAB isn't like those things, honestly. It's a dynamic budgeting tool. DH and I have joint accounts. We share our budget. We both have the YNAB app on our phones, so we can record spending and monitor our budget as we go.
YNAB makes you more conscious of your decisions in spending. Every time you get money, you allocate it. If you bump into someone and they suggest coffee and cake, that £10 will come from your 'sweets and treats' category (or coffee and cake, or eating out... Whatever you call it). That's fine if you have already allocated £10 to that category. If not, you have to make a decision - will you send less to savings? Will you spend less at the supermarket this week? Will you put less fuel in the car? - That £10 will have to come from somewhere. Instead of looking at your bank account and thinking "It's ok, I've just been paid and there's £800 in the account", by allocating all your money to your upcoming expenses, you have a true picture of what's 'available'. If you decide to go ahead and have coffee, that's great! Not a problem. But you'll be doing it in the full knowledge that you'll have to save less, put less fuel in the car, spend less at the supermarket, etc.
I apportion 1/12th of the cost of annual subscriptions/expenses each month. That serves two purposes. One, by the time the subscription is due, the money is waiting for it. No unexpected big bills. Two, it builds an account buffer, so if I do have a large unexpected expense, I have somewhere I can pull it from.
I need to work towards saving enough to pay for car insurance, etc., outright because that will save us money on the APR that is applied to monthly payments. In YNAB I can do that over time and keep track.
You're right that you can do all of this with a spreadsheet. But the reality is that it takes a long time. YNAB automatically imports all my transactions, it categorises them, and I can auto-assign the required money, so then I can deal with the rest of my budget very quickly.
We are on a relatively low income, with one wage (DC with SEN) but we have gone from running out of money, to just scraping by, to having a couple of tight weeks, to comfortably managing our money, to having enough budgeted to not have to worry about money. It isn't about how much you have, it's about knowing how far what you have can go and what your priorities are. There are people who genuinely don't have enough money, and they won't find that it is enough with YNAB or without it. But most people have enough, they just spend it badly, and YNAB shines the light on that.
What I don't understand is why people don't just try it. They give a 34 day free trial, so it's worth a go.