I say that yes, it's important for Sonic to have friends. It allows the character to be who he is without having to be everything the story requires of him and fleshes out both the world and the personality of the aforementioned hedgehog. The problem with the Sonic side cast lately is that it hasn't been controlled. While I haven't played Sonic Forces yet, I feel like the inclusion of some characters, like the Chaotix (as much as I love them) is pointless. They don't bring a lot to the table, in comparison to say Silver, who brings in narrative, or Tails, who has good character moments. Compare this to Sonic Mania, where the main cast was cut down to three (Sonic, Knuckles and Tails) and it works well. All three of those characters have a purpose - they all play so differently. Tails is slower, but can fly and can make for simpler platforming at times, but also longer jumps and higher ledges. Knuckles can climb and glide, which is also very different from the others. Sonic is very much the classic "Gotta go fast" style of the other games. Despite all three characters being in the game, they play differently.
Now let's look at Sonic Heroes. While three of the four teams (Sonic, Dark, and Rose) all play similarly for the most part, they each provide different difficulty levels. Each set of characters provides a different experience, as well as a different feeling (the more positive attitude of Team Rose compared to Team Dark makes the former feel more right for an 'easy' difficulty). They also all three provide different stories, giving narrative reasons for being there. I don't think I need to explain why I like the Chaotix being in this game compared with my concieved idea of them in Forces; they provide a completely different style. Espio can turn invisible. Their goals in each level are very different. Their story is a mystery, which fits in well with their motif as detectives. If any team deserves to be there (outside the obvious Team Sonic), they do.
So really, I like Sonic having friends, but I want it to be controlled. Give everyone a reason for being there - don't include everyone because you feel obligated to.