It's not the spec of the given plane that is the problem, justIN.
It's the concept of ENERGY you are missing out.
It's pretty much impossible to explain it in just one or two discussions, so I'll just say two things:
(1) Understanding the concept of relative E(nergy) differences between the planes, is the door to becoming a successful combat pilot in AH.
(2) Every newcomer has problems understanding this concept, and the lack of understanding often leads them to mistakenly assume that the game is wrong.
Here's a tip - it isn't.
Since we have no film to analyze the circumstances of what you've experienced, all we can offer you is some likely scenarios.
For instance;
(1) there could have been problems in the way you've maneuvered - making E-draining, unnecssary movements.
(2) during the "Boom" ('drop down') sequence of your attack, you may have misjudged how fast the enemy plane was already moving
(3) during the "Zoom" ('climb up') sequence of your attack, you may have pulled out too hard, burning a lot of E
(4) the enemy planes could have drawn you into a planned overshoot, and then may have moved into a position that "cuts a lot of corners", thus temporarily gaining distance
.. and etc etc etc..
Now, you may take a look at these scenarios and think "No, I didn't do that" - but trust me. Memory is fallible, and self-serving. A lot of times people say one thing, and then when we take a look at the film, they're just plain wrong. This is why filming your sorties helps.