That will only help if you have an issue within your home network. for e.g someone watching an HD video on a 5mbit connection which basically maxes it out, leaving none or very little left for games OR perhaps a torrent is sucking up all the bandwidth. This won't magically deal with bad routing issues on your ISP's side or fix Wifi interferance which also causes lag.
This will, however, provide a much more stable experiance. So for e.g if you get a ping of 100ms at idle and it tends to jump around to 150-200ms mid game, it will potentially make it a solid 100-110ms ping. If you have an issue with ping spikes when your family gets on the internet, this can definitely fix that. Alongside this if you can switch to 5Ghz wifi or to Wired Ethernet, you will get a very stable gaming experiance. The only thing holding you down after that will be PTCL's routing which isn't an easy or simple fix.
Personnel Experiance: On my own DSL connection I used to get very terrible ping spikes and in order to combat that I deployed SQM for OpenWRT, DD-WRT's QoS with fq_codel, and Gargoyle's fantastic effortless QoS on my TP-Link 841n V9 Router. In the end i still got ping spikes of about 10-50ms (A big improvement over the 100-300ms spikes) and it wasn't a totally solid experiance still. After many experimenting I came to the conclusion that my ADSL line just couldn't deliver any better since on the DSLreports test I only got a B at best, sometimes an A. I've got Fiber now and I also tried SQM on this connection. Needless to say I effortless got a ping. I downloaded a Torrent maximizing my connection yet my ping didn't increase for more than 1-5ms. So, even SQM or the world's most advanced QoS can't combat shitty situations.
For anyone who may not know what SQM (Smart Queue Management) is, it's BASICALLY a "QoS" feature on OpenWRT (A custom firmware for routers) that is meant to get rid of bufferbloat which in simple terms causes high latency w/e you're maxing out your connection.
Basically you have a limit, a bottleneck, which is 5mbit but it's on your ISP's side so you can't really control the flow of incoming traffic. What SQM does is that it limits the internet speed at your Router, making that the point of bottleneck and therefore the router has the ability to gain control of prioratizing the traffic which is then done through schedulers like Cake. This way it get's rid of bufferbloat.
If someone wants to, they can read all about it here:
For a simple version: https://openwrt.org/docs/guide-user/network/traffic-shaping/sqm
For a detailed version: https://openwrt.org/docs/guide-user/network/traffic-shaping/sqm-details