Will my ethernet adapter stop eveyone from getting WiFi if connected to my laptop?

Yes and no ... it really depends:

Wired is always the best for performance and reliability.

Every wired connection gets 1gbps (or 100mbps in older routers) for its speed, while the 300 mbps or 1300 mbps or whatever your router has is shared among all the current wifi users.

Thus by having a device hardwired it allows it to not pull from that shared wifi bandwidth. There is no situation where having a device hardwired will be worse then a device being wireless (assuming router and cable are functioning properly)

Now here is why it is also a "yes"

If you have a high performance router then it can handle many hardwired and wifi connections without slow down, however a cheaper end model of router will struggle to keep up with the demand, and thus the more devices using it in general (doesn't matter wired vs wireless) will degrade performance.

The number or active users (and their traffic demand) will also reduce the performance of your internet connection. Naturally if you have 5 people streaming netflix on a 50 mbps then there is going to be very little bandwidth for anyone else on the network (wired or wireless is irrelevant to this).

So in short, the more users you have the more performance drop you may see on your network, but wired will never slow you down more than WiFi will.