When I did this using MS Money or Quicken years ago, it took so much time to reconcile each month that I eventually gave up. And that was with automatically downloading transactions!
The idea that you could do this in a notes app and actually end up with an exactly matching total in app with the statement, where you don’t have to go back and review each transaction to figure out what you missed, is entirely implausible to me. First of all because the sheer number of scheduled recurring charges which may not be a fixed amount, second because the sheer number of quick charges that are run in a day where I am not stopping to open an app and record the total, third because my wife has a card on the same statement and even still sometimes borrows mine, forth of all because things like Amazon charges aren’t always totaled correctly when you first checkout (“estimated taxes”) and even then the total price on the invoice can be split across multiple charges, fifth of all because of various refunds which might occur due to a return made by someone else in the family for a purchase from a previous month, and similarly for orders placed on one day which aren’t shipped and charged until a future statement.
It’s an absolutely huge deal to precisely track your spending so well that the total balance in your personal tracker exactly matches your statement such that you don’t have to look at every charge on the statement and mentally account for it. It’s literally a multi-billion dollar problem and market opportunity.
That said, the frequent download is a crucial part. If I had to do this on a monthly basis it would be much harder because I'd have to put in an hour of work all at once.