It's not just Shazam but any app that uses the mic over Bluetooth. Like if you wanted to have background music playing during a Zoom call, or wanted to wear Bluetooth headphones while gaming and voice chat kicks in when you group up, etc.
It's a very annoying problem because the Airpods actually sound fantastic, but as soon as the mic kicks in, it sounds like crap. Same thing happens with my Sony XM3s or any other Bluetooth headset. The protocol drops to a shitty bitrate to support full duplex.
what you are describing is a universal Bluetooth issue. Windows suffers the same; some Android devices support proprietary codecs to slightly improve the situation but it's still sad we are still here.
It just automates the manual workaround: It tells your system to use another mic, not the bluetooth one, so that the bluetooth headphones go back to listen-only mode and doesn't have to operate in its inferior full-duplex mode. So you'd use the headphones only for hearing, and your computer's internal mic (or another external mic, like a webcam's or a standalone USB one) does the recording input.
I do that for all my calls and games already, but I just have to manually set it in the OS (and sometimes on a per-app basis). It only takes a second and usually remembers.
If the app were a one-time purchase I'd probably buy it just to avoid the hassle, but definitely not paying a subscription for something that's so easy to do on my own. As a compromise, I'd also be OK with a OS-version tied upgrade pricing, like you pay $x for the macOS 15 version, but when the next breaking OS update comes that requires an update, you can pay $y after the upgrade discount to get the newest version that works with the new OS.
The default behaviour is designed intentionally to 'degrade to the least-costly codec license' .. since the codecs available to the end user are one of the only ways that different headset/headphone manufacturers can differentiate, doing whats necessary to degrade to the least common denominator allows developers to route around the issues imposed on them by management: namely, don't promote the features of other headset manufacturers, needlessly.
It's a very annoying problem because the Airpods actually sound fantastic, but as soon as the mic kicks in, it sounds like crap. Same thing happens with my Sony XM3s or any other Bluetooth headset. The protocol drops to a shitty bitrate to support full duplex.