I installed pi hole on my raspberry pi, pointed my router to use it as a DNS server, even disabled DHCP on my router and activated it on pi hole
All clients in my network should get filtered traffic
Traffic doesn't get filtered. On my Mac using the router's address 192.168.2.1 as DNS server the traffic doesn't get filtered. Also the pi-hole admin console doesn't show filtered queries.
When on my Mac I input the pi hole's IP as DNS server, the traffic gets filtered and the pi-hole admin console shows filtered queries.
This normally indicates a router problem. Depending on the model of router, there are a number of ways the router can provide an alternate DNS path other than the Pi-Hole.
Look through all the menus on the router and look for other DNS settings (WAN, LAN, family-filtering, DNS pre-binding, DNS caching, dynamic DNS, IPV6). You may have to solve this through trial and error. Sometimes a setting is buried in a gray-out menu, and when you select the menu and make it active you find an underlying option that is causing the problems.
A second potential problem is DNS caching on clients. This does not appear to be the case on the Mac, since when it goes directly to Pi-Hole for DNS it works. But, Windows PC's can hang onto DNS settings unless you flush the DNS cache.