"I disagree that other people in the class haven't improved. Here are examples:
1) Midoriya (obvious)
2) Bakugou - has matured mentally shown by his acceptance of Deku and his attitude toward Deku and All Might's relationship after their fight. Dude has also come up with about 3-4 different supermoves during their supermove training, examples being the Howitzer Impact, AP Shot and AP Shot: Auto Cannon. We also see his brand of being a hero when the League of Villains kidnap him in an attempt to make him sympathetic to their cause. He proceeds to evade a group of 5+ villains by himself for an extended period of time
3) Todoroki - mentally matured by analyzing his relationship with his father and accepting him - in turn, he has been able to simultaneously both fire and ice
4) Iida - went through a trauma when his brother was incapacitated by Stain and developed further mental fortitude - given his ability, most of his training has focused on extending use of his quirk. He DOES have one new ability - Recipro Extend
5) Tsuyu - mental progression after the OfA vs AfO battle, when she told Kirishima / Todoroki that they would be villains if they just did whatever they wanted. While her straightforward way of thinking is usually very useful in breaking down complex problems, she recognized that there are somewhat grey areas afterward during the UA dorm room competition arc. She has continued to develop more abilities similar to a frog, such as camouflage
6) Kirishima - was part of the task force to take down Chisaki, where he faced a life / death situation against a villain practically alone, with only his hardening quirk to help him in the fight. This showed the developments in his quirk training and mental toughness
7) Ochaco - up to this point, her defining moment was turning down Deku's help before her fight with Bakugou and forcing him - someone considered among the top 2 in Class 1-A combat ability at that point - to fight her completely seriously
Tokoyami - we've seen his relationship with Dark Shadow in a number of situations, from the sports festival where his major weakness is revealed to the training camp arc where Dark Shadow goes insane. He's created a new move that allows him to "wear" Dark Shadow in close combat
9) Yaoyorozu - while initially admitted by referral, she fades into obscurity shortly after the beginning of the story with no real feats. This is addressed during the final exam arc where she has to overcome her own anxiety and make split second decisions with confidence in order to defeat Aizawa. Hell, the anime has an entire episode dedicated to this titled "Yaoyorozu Rising"
10) Kaminari - we see him finally able to use his electricity effectively during the provisional license exam where he comes up big against Shiketsu
The above are some of the progressions of 10 characters in Class 1-A: there are only 20 students total. While not everyone has been given the same depth, two of them have been the focus of major story arcs (Iida / Stain, Bakugou / Kidnapping) and others have had key moments or entire episodes dedicated to them.
Frankly if the above doesn't convince you that there has been real attention paid to other students' progressions outside of Midoriya then I think we'll have to agree to disagree. Most of your comments seem to imply that MHA is making poor decisions for the long-term; this will prove itself out over the coming years, and will likely be settled 10 years from now when MHA is either mentioned in the same sentence as OP & HxH or instead compared to Bleach."