Technically there's 3 movies and 2 movies. Being broken by the reboot ceased the continuation of the characters progression but I take your point of all 5 being spider-man movies not spider-man and other heroes movies
Since this won't likely be rebooted again so they can now develop the supporting characters more. Instead of adding in non-Spidey characters who are already developed they should focus on using that screen-time on developing the supporting characters, of which the Spider-Man franchise has tons of known and already beloved characters to utilise.
I'd much rather see Flash develop from Bully to friend to Soldier to Veteran to superhero than see a slew of interchangeable cameos of non-Spidey characters over the next few films.
IMO Spider-Man 2 remains the best Marvel movie as it has near-perfect mix of amazing action, shifting tone, romance, character depth, supporting roles each with their own small arcs and great drama and performances.