disk utility does not see my time capsule

Disk Utility can only work with either the Mac's internal drive or any drive directly connected to the Mac. It cannot work with network attached drives. That includes the Time Capsule's internal (or an external USB drive attached to the TC) or a NAS.

You would literally need to pull the TC's hard drive out; install it into a drive caddy, and then, attach that caddy to your Mac, in order for Disk Utility's First Aid option to work properly.

If your goal is to "repair" the TC's internal drive, then use TM's "Verify Backups" option on this drive. To access this option, hold down the option key, and then, click on the TM icon on the macOS menu bar.

It's not supposed to. The Disk Utility won't see network drives such as it.

Use the AirPort Utility to repair or erase it.

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Disk utility sees my other drive, and that is why I was asking.

Your "other" drive is likely a USB drive that is connected directly to a Mac, which would make it a "local" drive. The Time Capsule is a "network" drive which connects to your network, not directly to a Mac.

Disk Utility can only "see" a local drive, not a network drive.