A sound designer once showed me an interesting psychological phenomenon about synchronizing foley for footsteps (which I'm sure has a name that unfortunately I've forgotten).
They said that if you have 1-3 people walking on screen and you can see their feet, the footstep sounds have to match exactly. But if there are more feet than that, you can just play an almost random assortment of footfalls with no specific sync and the brain won't really complain.
There's kind of a threshold of complexity where our brain checks out and says "sure, I'll buy it".
So you may be able to take advantage of this.
Keep a separate channel around for bombs in the player's immediate vicinity, or bombs the player themselves placed. Those should always get unique sounds matched to them.
For all other bombs, not only can you attenuate them by distance, you can start to chunk them down by how many have gone off recently. Say the first and second "other" bomb to go off in the past 1 second interval get bespoke sounds each. But if a third bomb goes off within a second of two others, don't play a full explosion just for it. Instead, blend in a background rumble track representing "ambient explosions".
You can scale the loudness of that ambient track (or blend between different versions of it) based on how many "other" bombs have detonated in the recent time window, and fade it out entirely once that number drops down below 3 (or whatever threshold you choose).
If that same footstep foley trick applies, the brain should see a lot of explosions on screen, hear a lot of explosions in the track, and say "sure, I'll buy it," without attending to whether it can pair up every single on-screen flash to a specific boom.
This lets you cap the complexity of the soundscape to the ambient layer plus
n individual booms, where you can tune
n to your liking. You can also custom-design that ambient track (or its various layers/versions) so it sounds more pleasant than a lot of the same explosion sound repeating, and doesn't distract from the nearby bombs the player needs to focus on. (Though not being a sound designer myself, I can't detail exactly how you would do that).
That may not be a complete solution, but it's a strategy you can try to get a bit more granular control over the soundscape, and help you prioritize the most important sounds for the player to attend to.