Drogon is more experienced.
There is a similar Question over on SFF.SE with a nicely summarized answer.
Drogon is the biggest
Drogon is essentially the big brother of the
three. He's the largest, potentially the fastest and most probably the
strongest; he's the alpha.
Drogon has Dany in the pilot seat
It would make a lot of difference
that Dany is the one riding Drogon, able to give commands, and steer
him better than the other two may.
Drogon has the most combat experience
Being Dany's main ride, Drogon
has experienced a lot of attacks, he has gained the most experience
under attack than his two siblings.
Viserion was hunted by the Night King
Olympic level javelin throwing
is an understatement for this guy. The Night King took down Viserion
as they were retreating with an epic throw of his spear. He's
powerful, that spear was travelling very fast, and hard. It pierced
Viserion exactly where it needed to to mortally wound him.
Rhaegal was injured already
In the scene where Rhaegal is shot down by
Euron's scorpion, we can see that Drogon and Rhaegal are flying in a
tight, low and slow formation. Rhaegal is visibly injured, his wings
torn from the Battle of the Long Night. This makes him slower, and a
much easier target.
Besides, Euron had the element of surprise; he could take his time
with his shots and make it count. Notice how once alerted, Drogon was
able to evade the rest of the arrows?
Drogon was in fact hit once Recall in the Seventh Season, Drogon is
hit by Bronn's scorpion, severely damaging his shoulder. So he's not
Why is Drogon so much better in battle than Rhaegal and Viserion? - SFF.SE
When Rhaegal is killed it seems apparent that Dany wasn't expecting the Scorpions in that magnitude or seabound and she was also already angry about losing one dragon, why risk the other?
In S8E05 Dany wasn't looking to intimidate she was looking to negociate (or at least Tyrion convinced her to).
I don't want to see this city burn. I don't want to hear the screams
of children burning alive. No, it is not a pleasant sound. I-- I don't
want to hear it. Help me save this city. My lord, I am only a
mouthpiece for our queen. TYRION: Your queen. Cersei is Queen of the
Seven Kingdoms. You are her subject. Her reign is over. You understand
this. Help her understand it.
Game Of Thrones, Season 8 Episode 4 (The Last of the Starks)
A dragon pacing around would have put everybody on edge and probably decreased their chances in successfully negotiating a truce. Furthermore, if Drogon had been sitting in the front lines with Dany, and they had chosen to attack he would be an easy target for the dozens of scorpions. So, no strategic or diplomatic advantage would have come from Drogon sitting front and center.
In S8E05, Dany (and Drogon) knew what they were getting in to and were now preparing to evade the shots fired from the scorpions and knew not to come from in front but go straight down the middle and spend as much time as possible circling The Iron Fleet to make aiming as hard as possible.
So, no Drogons powers weren't downplayed he was simply lacking the preparation and experience up until S8E05.