My take...
1) The population that made up their primary customer base has moved. As we have seen with redistricting, there has been significant population decline south of Forest Hill, which is the delivery area for Avanti's on Main.
2) There are a LOT more restaurant options today, in the nearby area, than there were ten years ago. If you are not feeling it for average italian food, you got many choices now.
3) Ten years ago, you had limited delivery options... pizza, avantis, some chinese places, and that was about it. Now you have GrubHub, Doordash, Uber Eats, and their like facilitating delivery for nearly every restaurant. You want McDonalds delivered? Done. You want Dac's Smokehouse delivered? Done. Jr's Chicken? Done. One World? You bet! Thanh Linh has been doing crazy amounts of delivery, that they never did before. Choices choices choices...
4) Even before the pandemic there was a decline in people working downtown. The main street location did a robust lunch delivery business. They would quietly open at 10a to get it rolling. All that has nearly gone away. The pandemic and the shift to work from home has only made it worse.
5) Finally... staffing... the Avanti kitchen is tight and cramped. The pay seems to suck. Management is inconsistent. There are more desirable places to work.
The intersection? Nah. Sales Tax revenues for the area tell a very different story. That intersection has been good for the area and good for the city. Expect more of it, when they redo Main and redo Western all the way up.