Hello and welcome to Feedback Quest 9! My name is Hythrain, and I'm one of the hosts for this lovely event! I'm also one of the streamers, so both the game and this feedback are being done live! If you want to see the see the VOD, let me know and I'll link you to it when it's uploaded to YouTube!
This is a great way to reinvent Breakout (it wouldn't be Pong as Pong would have you play horizontally rather than vertically)! I honestly found this a lot of fun to play! I could see myself getting addicted to this. There isn't even a lot of feedback I feel I could give for this, but I'll try anyway.
So first, I think everything should start smaller and balls should move slightly slower. The reason why is because otherwise this game can get very crowded very quickly as new enemies and effects and projectiles are added in. Doing this you make the arena "bigger" and leave yourself more room to prevent clutter. If you want, you could do boss fights zoomed back in to make them more engaging and challenging.
Other than this, I have two recommendations for changes to relics. My first recommendation is that you should remove relics that increase your main ball speed. To me, these feel like nerfs instead of buffs as a faster ball makes it more likely you're going to miss the ball and thus take damage. Instead, any relics that increase speed to balls should only do so for extra balls as you can't get hurt for not bouncing those back with the paddle (which I'm very glad for. Otherwise, extra balls would ALSO be a huge nerf).
The other recommendation is that you should make it that relics that only affect other relics should require having at least one of the relics they affect before they can show up. For example, any relics that specifically affect extra balls should only show up once you have a relic that gives you extra balls, whether these are fragile balls or solid extra balls. That way, the player can't get relics that they can't make use of until they have the required relics.
The last thing I can suggest is to have a means for the player to heal themselves without needing to get just the right relics to do so. Right now, you either have to get a relic that heals you every 3 levels or just get one that restores your health. While I think you should still keep the heal every 3 levels relic, I would say you should instead put in a currency system (either enemies can sometimes drop the currency and you have to try and catch them much like the power-ups in Breakout, or you get a set amount of currency for each level cleared that increases by a small amount up to a certain level) and a shop where the player can purchase temporary upgrades that last for a set number of waves and the ability to heal themselves. You could even make it that the player can purchase permanent upgrades to increase their max health while that the cost of healing increases with the player's max health.
I hope this helps you out!