Libre office is a fine tool, I use it myself. Calc is a somewhat capable spreadsheet application, although it has its fair share of issues and quirks. But that’s true for most software these days, although I do wish the windows wouldn’t be on a random monitor at a random location and random size all the time.

However in this case they state their solution is a Google Sheets and Microsoft Excel competitor. These are tools one uses online in a browser to access files stored on the server of the provider. That’s pretty different from what Libre Office Calc offers. It’s a bit confusing because Microsoft calls their app Excel, which can refer to the online service or the offline local app. But with Google sheets it’s clear it’s the online service they refer to.

So the comparison isn’t a straight one. If a local app is an option, I would prefer that over an online service. So Libre office is the way to go. But many people prefer something that’s available on any device, including underpowered tablets and phones, and want their files to be accessible everywhere. For those people it’s good to have competition to Microsoft and Google.

or only office, or crypt pad.

If they actually cared about privacy, they would just contribute to CryptPad and host an instance.