As others have noted, it depends on the system. VTTs are often thought of as being oriented around battlemaps and visual aids, but you can play theater or the mind with character sheets in a VTT. If the system support is rich like pf2e in Foundry, DnD5e/SWADE in Fantasy Grounds, or any VTT with strong support for a particular system... then you'll have access to great sheets, combat trackers, and automation.

For niche systems, yeah... spreadsheets are the original tool for non-programmers to track stats and math. They're great for building custom sheets. They don't have the flexibility of a true programming language to create custom UI and really rich automation. But they are very very good, and can be better than a VTT with poor system support if you don't care about visual aids.