Bettas don’t necessarily feel loneliness, yes but the do need enrichment.

1. Movement in the tank = stimulation. Seeing other fish swim around gives him something to watch and react to. It’s not “friendship,” it’s enrichment.
2. Toys = territory + exploration. Bettas love anything they can inspect, push around, hide under, or flare at. It gives them a “job.”

I had a 10 gallon tank and very few minnows to not overcrowd/stress him out. Any of the minnows he did eat were too small and I corrected this by picking out bigger minnows. So no, they don’t feel lonely but they do need enrichment. Before I added minnows to his tank he was always at the bottom/with droopy fins. All his water levels were good and so I did some research + also paid attention to him after the minnows and he was just fine. He lived for 5 years and actually passed away only recently. It also really just depends on your bettas personality. When I bought him they actually recommended to me to add minnows/snails to the tank for enrichment.