I have seen many articles online about using a phone or computer to act as a Bluetooth-WiFi(internet) bridge, where you can share the internet connection with other devices over Bluetooth. But I have not seen any generic stand alone devices that would allow this same function. I have seen ones for specific IoT devices that allow Bluetooth light bulbs and such to be accessed over WiFi but not a generic one. Has anyone seen such a device?
Bluetooth is a proprietary technology which is managed by the Bluetooth SIG. Unlike "Wireless A/B/C/N/AC", which is the networking technology standardized by IEEE, Bluetooth is tightly managed by this group and specific patents are required when making something Bluetooth compatible. This means that the "stack", which manages to what and how a device can connect to other BT devices, is often proprietary to the device itself.
You can experiment with this by purchasing a Chinese-local Bluetooth headset designed for phones and trying to pair it with a Dell laptop that has integrated Bluetooth. Chances are, your device won't pair, and you'll have to download the Chinese company's BT stack to your computer and install it. This often interferes with the existing stack that comes with Windows and may create new problems.
This, and the inherent short range of BT, are why you see devices that will take commands via WiFi and relay them via Bluetooth, but not accept commands via Bluetooth and convert them to a traditional WiFi signal. It takes a machine with a compatible BT stack and its own connection to a wireless network of some sort via its own wireless adapter. That's why you're seeing the articles that you're seeing; they do exactly that.
Obtaining the BT patent and permissions to build a router that does this specifically and selling it as a consumer item faces hurdles manufacturers wouldn't want. BT is intended for short-range, so any product like that would immediately catch flak from misunderstanding consumers for being terrible once they're out of the same room.
A Bluetooth Router which can connect to your WiFi router, however, does exist. If you read the Amazon reviews for it, you'll find that the low-star reviews all involve problems I've described here (failure to pair due to BT stack, range issues past 30 direct feet, etc.).
Your best bet is probably to use a computer or phone that will manage its BT-connected peripherals as peripherals and just give other things access to those peripherals via Wi-Fi.