You mention a few things that happened but you didn't provide any details which might shed some light on the problem.
1) You said the technician tested the speed using Ethernet. What was the result? Was the speed the same as what you were getting on WiFi?
2) You said you now have smart steering turned off and have 2 separate SSID's (one each for 2.4 and 5 GHz) Which one are you connectect to when you do your speed tests?
3) You say "gave me a “secondary router” to help with the amount of devices" and then you say "Just on my phone, being the ONLY one using the wifi". This is contradictory. Do you have a lot of devices on the WiFi or not?
If you are consistently getting good Ethernet speeds then your Internet speed is not the issue. As you suspected it's your WiFi.
What model phone you have?
Do you have other WiFi devices and if so are you able to do speed tests on them to cmpare?
How many other WiFi SSIDs do you see from your phone? Could be a channel congestion problem.
For what it is worth, I am on Internet 75 with a bonded modem (two copper lines), and I just tested my ethernet connected PC. It came out at 75 Mbps, with a 4 ms ping. My iPhone 8 which is connected to the 2.4 GHz SSID just tested as low as 34 Mbps, and as high as 59 Mbps, 10 ms ping. It seems quite variable on the WiFi, and quite consistent and high on the ethernet.
I used to have a 50 Mbps modem, which was also bonded. It has some speed issues when it was first installed. One tech that came to the house tested the two lines and decided one was weak. He said there was a "tap" on the line that should not be there. I don't fully understand it, but I think that means when I was not using the one line somebody connected another line to it (and probably should not have). In any case it was repaired and the signal strength improved. It is something you could ask about. However, if you are getting good ethernet speed, then it seems it is a WiFi problem within your home.
I think to get 50 or 75 Mbps they have to use two copper lines coming into your house. That requires a bonded modem. They split the signal between the two lines at the wire centre, and then bond it back together at your home with the bonded modem. At least that is my memory of what they used for the 50 Mbps service. I switched to the 75 Mbps service when I called to complain about the price of the 50 Mbps. As a result of my call I got the 75 Mbps service for less than I was paying for the 50. I am also on Telus Optik, so perhaps the need is driven by the combination of TV and internet...