In the Star Force series, you do not play as a boy who befriends and owns Mega Man, You're Mega Man, Mega Man is the combined form of Geo and Omega-Xis.
And in all honesty after replaying both the Battle Network and Star Force series, I'd argue there's more differences than you seem to be aware of, and I'd also argue that Star Force is better overall.
The storytelling in the Star Force trilogy is some of the best within the entire franchise, Geo is easily the most fully developed protagonist in the franchise's history, and Star Force's balance of light and dark tones, as well as it's surprisingly great characterizations are very commendable especially in comparison to it's predecessor that barely focused on such concepts.
Battles in Star Force are streamlined, but as a result they tend to be much faster paced, emphasize offensive play, and are a ton more accessible, all of it's mechanics highlight this(MegaAttack(Lock On) Drawing 6 Cards instead per turn instead of 5 chips, actual hitstun, Battle Cards have no letter codes meaning you can actually combine any card together in a single turn, allowing Mega Man to fight essentially however you want him to, Super Moves upon successful counters, Shield Cancelling, Brotherband cards and boosts, The new rapid firing auto charging Mega Buster, the 5x3 grid layout and more) There's enough nuance to each one of these mechanisms for the game to have a ridiculous amount of depth, even if it might not reach the heights of it's predecessor in that department, I don't think that was the point, MMSF was meant to be a fresh take on MMBN's formula, and with all it's improvements and mechanical differences that's what it felt like, not a re-invention of the wheel but refreshing and different enough to be it's own worthwhile experience with it's own identity.
Even the map design found in the Star Force series is much more intuitive than that found in it's predecessor, and it's stage design differs in that it drops the focus on puzzles in favor of a more straightforward design having the player fight through obstacles and enemies themed after the area boss, occasionally fun mini-games come in, but don't overstay there welcome and never break the pace.
Mega Man Star Force is an criminally underrated series that seriously deserves more credit, It's very easy to misunderstand, but when you take the time to look at it on it's own merits rather than what you personally expected from it's predecessor, it's very easy to see that it actually was a very good series, that really just came at the wrong time.
