Nailed it

I have to inform that the crux of the problem with Spike - and episodes featuring him - is that you need to drag everyone down if you want him to shine at all, and these are notable examples in G4 where that happened: Equestria Games, Gauntlet of Fire, and Times They Were a Changeling.

In Equestria Games, Spike were unabashedly stealing every credit for himself in spite of all hard work the others had done: (1: Cadance - who's been providing a shield all over the Crystal Empire the whole time since Sombra's arrival - got no credit. 2: Pinkie Pie, Rainbow Dash, Fluttershy, Rarity, and Applejack - who entertained the Crystal Ponies with a Crystal Fair to charge up the Crystal Heart - got no credit. 3: Twilight Sparkle - who figured out the Crystal Heart's hidden location, found the hidden passage to it, made it all the way up to the top of the stairs with her up-side-down magic, and risked herself failing Celestia's test by forcing Spike to deliver it - got no credit.) All Spike did - to get all credit - was to run a short distance until he tripped over and fell. Even Shining Armor didn't receive any credit for saving Spike and the Crystal Heart from their fall. Frankly, Twilight and Cadence were the ones who saved the day, not Spike.

Later on, after Spike miserably failed to sing the Cloudsdale Anthem, he managed to redeemed himself - and "saved the Crystal Empire twice - by melting an ice-cloud that wasn't even big enough to crush the entire stadium. Why didn't someone come up with a contingency plan for this situation? This "magic-disabling spell" was applied to the unicorn-spectators/competitors to prevent them from cheating, but the head of security though it'd be a good idea to disable Equestria's officials' and the princesses' magic, as well, as if it's believed that they'd cheat themselves.

In Gauntlet of Fire, Spike got a chance to save the day by preventing some teenage dragons from invading Equestria to steal the ponies' beds. Garble wanted revenge on the ponies for "crossing" him without explaining how/why.

Torch and Ember was added into the show because they were only needed for the episode's sake. For example, Ember's purpose for being introduced was only to take Spike's place as the new dragon lord, so he wouldn't have to stay in the Dragon Lands.

Neither Twilight or Rarity could handle a couple of teenage dragons, even though they already faced other foes, such as the Changelings in Canterlot Wedding.

In Times They Were a Changeling, Spike was the only one who knew that befriending the Changeling was the right thing to do while everyone else was like: "Nah! That Changeling must die!"

Spike becoming the "Brave & Glorious" and a "Friendship Ambassador" was to have everyone else thrown under the bus. So, in the end, Spike's "character development" actually backfired.