There don't seem to be a lot of choices for sit down restaurants.
You say “sit down” restaurants, which after reading all the replies I’m not sure exactly what you mean since you mention Troubadour Tavern, Jolly Holiday, etc. Most restaurants have seating areas. I specifically mentioned “table service” restaurants as a server will take your order and bring your food to you. There are quite a few but you will have to stay on top of making reservations:
Plaza Inn at breakfast only
Carnation Cafe
Blue Bayou
Cafe Orleans
River Belle Terrace
Wine country Trattoria
Carthay Circle
Lamplight Lounge
(That’s all I can think of off the top of my head)
Plus there are many options at the hotels and in DtD.
Disneyland cast members can carry a tray for you to a table, if you are at a restaurant with a dedicated eating area such as Tiana’s Palace, Tropical Hideaway, Hungry Bear (which you aren’t interested in), etc. It would work best for you or your traveling companion to get the table while you’re waiting for the food to be ready, because it’s too much to ask the cast member to find a table when there aren’t any available. Be aware that mobile ordering leads to these seating areas often being full of people waiting for their orders — there’s nothing wrong with doing that. Places with more seating, like Hungry Bear, are easier to get tables at than Bengal BBQ, which doesn’t have enough seating even with what they’ve added. In the most crowded seating areas it helps to be willing to hover, to make eye contact with people who are gathering up their trash and appear to be leaving, and to ask those people if they are leaving and you can have the table.
Jolly Holiday is one of the hardest quick service locations for me (not food carts, just QS) because the seating area is raised and you have to find a place to maneuver your wheels, plus the tables are closely packed. Actually, closely packed tables can be an issue in many seating areas, I just find JH to be a little worse.
I guess the question is, how do you manage at fast casual or fast food restaurants, food courts, etc. that aren’t at DL? That’s what you can do at Disneyland, with the extra benefit of Disney cast members being far less likely to be unable to carry a tray for you due to staffing issues (e.g. a cashier at Chipotle can’t leave the line to carry a tray, but a DL cast member can quickly find someone who can).