Be unique in your voicemail greetings, add a human touch when creating the message.
When recording, choose a quiet area, speak clearly, and use your full name (first and last).

All that makes configuring and managing home routers very difficult for IT personnel, but they'll still be faced with that task because if employees run into conversation problems over their softphones, their first call will be to the IT help desk. Shunting them off to the VoIP provider, or worse, the ISP isn't a good idea either. It'll likely cause employee frustration since those outfits won't be familiar with your company and they'll either refuse support or it'll take a very long time.
While the exact features offered in any particular UCaaS solution can change radically from vendor to vendor, most include options for video conferencing, shared meeting and online collaboration tools, integrated faxing, mobile VoIP integration, and device-independent softphone clients. That last one is especially important now because it means that your employees can download an app to their personal smartphone or company laptop and that app will mirror all the functionality of their corporate phone, including responding to calls coming into your business phone number and their extension in particular. For folks trapped at home by the pandemic, that's a perfect solution.