Since you are aiming at more casual users, consider intuitive intelligent audio controls. Beginner and often intermediate users often do not understand the importance of good audio in a video. When they do it still takes a steep learning curve to understand the complexity and nuances of even the basics.

Most video editors don’t help users with audio.

Ideas:

Templated signal chains for individual audio tracks that include simple things such as gate, subtractive eq, compression, additive-eq

Templated master audio signal chain that can include simple compression / limiting , eq, and maximizing with a specific target LUFS in mind (based on where the user intends to upload as different sites have different ideal loudness)

Level suggestions for tracks, based upon if they are dialog, music-bed, room tone etc

Automatic level adjustment to bring the music bed up and down based on other tracks. Or simply the ability to generate suggested level automation.

Actually, automatic suggested level automation on any track independently would be really useful for things like dialog and interviews.

Not specifically audio, but being able to output multiple different renders depending on target website with a single click. (Ideal container, codec, resolutions, ratios, LUFS, etc). Even with predefined templates in other editors I have used, I still need to select and queue each render specifically.

Of course these suggestions are very reductive, but even the basics go so far in making a video not be bad.

Ultimately bad audio can make the best video unwatchable. Give the user some optional guard rails.

Oh yeah, don’t forget to transparency account for audio processing latency. Else lips won’t sync with dialog. Saw that happen with a beta version of an editor a few years back when they added VST support.