Making it 2-player would be like a kind of “super-pong-battle-arena”
Both sides have to protect their bricks while trying to destroy the others ones.
That would be a whole new direction.
However to make your current version instantly more interesting would be to enhance the computer Ai to make it seem a bit more human.
Vary the speed if its movement. Don’t let it move always towards the ball.
Make it seem it watching the ball when it is in the other half to quickly move toward it when it is coming into his own half of the field…
Let it appear to become excited or nervous when the ball gets to a certain amount of speed.
Things like that.
Since your concept limits what the bricks can do to to spice up the game (i.e. no powerups changing the play), beefing up the Ai seems to be a good idea,
Utilizing the big space between the players could be interesting.
A gravity well, influencing the ball?
Sporadic health “bricks” popping up, restoring lost bricks on hit?
Additionally “old-style” powerups floating from top to bottom from time to time?
Also it may be a good idea to give the AI the ability to buy and use powerups as well.
Closing the gap between the players by making the bricks a bit larger can change the whole feel of the game.
Visual presentation can be a thing to spice up the game too.
The pink borders are not particularly inviting.
The bricks are a bit flat looking, as well as the player-paddles.
Adding some more effects maybe.
Some moving pictures related to that:
Hope some if all that sparked your interest