After checking this site that maps all the carrier towers I've concluded that Telus/Koodo is not investing in mobile towers like Rogers and Bell in Markham. 

https://www.ertyu.org/steven_nikkel/cancellsites.html?lat=43.899191&lng=-79.240308&zoom=14&type=Roadmap&layers=brt&pid=17

I know that I'll be switching because it's frustrating using mobile data here, it's not even specific dead zones, it's all of Markham I get problems. There's maybe 2/3 less Telus towers compared to Bell/Rogers. Sad.

For anyone thinking about switching to Telus/Koodo in York Region, I'd caution to stay away. 

There seems to be some modem issues with the Google Pixel 7. That may explain why you are getting a poor connection. Have you tried using another phone to see if you are getting better coverage?

It is also worth noting that Bell and Telus are sharing the same towers, so you would experience the same kind of issue with them. 

Interesting, I joined the Android Beta and it upgraded me to a beta build to see if it would fix my issues.

I was on it for a week and it still caused me grief. Mobile data was slow as before if not worse. 

I spoke with Google customer care and they said they couldn't help since I was on beta software. They suggested I opt out and reinstall the latest stable. 

So that's what I did, not knowing that leaving Android Beta meant a complete wipe of my phone and had to do a restore. Eg, the phone would be clean wiped and then go through restoring apps, have to login again, setup all my icons on home screen, wallpapers, personalized settings. 

Overall it was a good time for me to get rid of unwanted apps that I've accumulated throughout the last 5+ years. But most importantly, it fixed my mobile data issue! Everything was snappy, apps loaded without issue even with 30% signal, it still loaded. 

I felt that it was similar to having to reformat a 10 year laptop that's been upgraded multiple times and a lot of legacy data/settings has been migrated and causing problems. 

A clean wipe once in a while is good, even on an android phone. 

Hope this helps others and worth a try. Last resort as it took a while to get the phone back to where I wanted it. But also a good opportunity for clean up!