Documentation Landing Cleanup

Description

This PR does two main things:

1. It simplifies and cleans up the Documentation Home page (see screenshot)
2. It makes some minor edits to other docs pages that were observed to be confusing during user interviews

New Docs Home:

While I think there is more that could be invested in the docs over time, I don't think further improvements are on the "critical path" to getting more signups. Further changes to the docs can wait until we observe issues with setup and technical questions.

Checklist

• the MR description has been reviewed
• this MR contains text changes and they have been reviewed OR there are no texts changes
• this MR contains GUI/CLI changes and they have been reviewed OR there are no GUI/CLI changes
• this MR contains API changes and they have been reviewed OR there are no API changes