Depreciation is past capex, not future capex. You could argue that the two are equivalent, because the assets being depreciated will need replacement in the future. But:
1. The assets' useful life may be longer (or shorter) than the depreciation schedule.
2. The future replacements may cost less (or more) or just not be needed at all.
Technically (from an accounting perspective), yes. Practically (from a financial/economic perspective), not quite.
Past capex is a sunk cost. Investors care about future cash flows. If you strip out depreciation, you’ll be surprised by the bill when your machine breaks down. (You may still be surprised. Life is unpredictable and depreciation schedules are an estimate. But that’s one of the problems the concept tries to solve.)
Income statements include things like depreciation. That's real, in a sense. It's future CAPEX. But for the present health of a business, particularly a levered one, cash is king.
One way to think of it is in time frames. Cash flows are immediately relevant. If they're out of whack, it's an urgent problem. (They're also the most difficult to mess with.) Income statements are longer term. An unprofitable, cash-generating business may have structural issues with its PP&E, or it may be overleverd, or a bunch of options might have been issued or exercised. Balance sheets are the longest-term statement. (They're also the easiest to mess with.)
Keep in mind, too, that income statements for investors are different from those prepared for the IRS.