Seeing a much lower speed than anticipated can certainly come as a shock! I can confirm that Ookla speed test is accurate. I'll be happy to help identify why you're unable to see higher speeds. To begin, are you able to complete a speed test with two wired devices at the same time? Alternatively one wired device to the modem and one wireless (using 5G). Once done share the results with us and we can go from there.
I have documented my speed problems at length here in September/October or 2019. In summary I have seen speeds of about 300-350M for many months now (I have the 1G plan). My average speed for January 2020 was 320.71M with over 150 speed tests).
I have had Rogers techs here 4 times and every one of them have had exactly the same speeds when they do their tests. They have reset and swapped out the modem multiple times with no improvement.
They have tested the local drop with their equipment and told me that the problem lies there - it is incapable of over 500M and with a number of local users I'm lucky to get the speed I do get.
My issue is actually with the speedtest itself. I have been using the browser version for all of my testing but I have tried both the Windows (install) version and the stand-alone line (CLI) version. While the browser version (no matter which browser I user) shows a speed of 300-350M, the CLI and the windows version show over 800M. I can't understand how this is possible.
Also - regarding doing multiple tests concurrently - I have run as many a 4 tests at the same time with wildly different speeds that average well over 1G and has reached as much as 1.6G (!).
I am beginning to think that the speedtest is highly unreliable.