Band 12 is not ment to be fast per say, its ment to help fill in coverage and reach locations that higher frequencies just can not go. I also want to point out that the dots or bars that show signal strength are never a accurate way to tell what the quality of the connection is. You must also remember that band 12 operates on a 5x5 block of spectrum since that is all T-mobile has for that specific band while other bits of spectrum like band 2 or 4 operate on 10x10 blocks or higher. Despite the nerd the best way to think about it is like this. Band 2 and 4 are like a 4 way highway with a theoretical speed limit of 80mph but once you taper off to band 12 your back to a normal road.
Just remember that things will get better with time as T-mobile gets there hands on the 600mhz that they acquired from this most recent auction and that in the mean time you have some form of usable coverage which is better then nothing at all. Which without band 12 would of been the case for you more likely than not.
I understand that the number of bars isn't actually a precise representation of signal strength, although it's usually useful as a relative indication, ranging from "solid" to "nil."
And to say that band 12 isn't "meant to be fast" is really strange, since users don't get to choose what band they're going to connect to at any instant, and, like me, expect to get essentially the same kind of performance from the same indicated signal.
The promise that things will get better when the 600MHz band is available is essentially what we were told when we were waiting for the 700MHz coverage on band 12 to be turned on.
Well technically speaking things did improve considerably when band 12 got deployed because it expanded T-mobiles coverage significantly and added slightly more capacity. Also as mentioned before this acquisition was pretty much solely ment for the expansion of coverage since there are just some places higher frequency's don't do well (I.E. think highways and wooded areas). I'm sorry if you were informed in a different manner on how band 12 was supposed to behave or what it is supposed to deliver but in this moment in time there is not much T-mobile can do. I should also add that its actually with all carriers. If you were to be stuck on Band 17 which is what At&T uses alot you would see slow speeds in my area think 8mb but if you happened to be by a tower where you could CA bands 17 and 2 for example then you see like 60mb down.
Honestly though your speeds are actually pretty good since upload speeds are not to relevant to most use cases for the average user. As far as websites not loading there are variables that need to be accounted for before saying it was the LTE connection.
Also the 600MHz spectrum is different from the band 12 situation due to the amount on average they acquired. So theoretically speaking they should be able to attain similar performance to its band 2 counter part due to the sheer amount of spectrum and other technologies.
Sanibel Island is a place with coverage issues. They have highly restrictive zoning laws there. There's just one cell tower to serve the whole island. Much of the signal on the eastern side of the island actually comes from a tower at Punta Rassa, across the bay. All the carriers are in the same boat in this regard. The whole SW Fla market is one where T-Mobile has historically had coverage problems, many of which seem to persist even after overlaying band-12.
Since I don't know where you live in Minnesota, I can't say what signal's available there. If it's a band-12 only area, it will be limited to what 5x5 LTE can accomplish and 10 Mbps down sounds about right.
The Pixel has Carrier Aggregation (CA) which allows it to use more than one LTE signal at once. If you are in an area with a good band-12 but a marginal band-2 or 4 signal, the Pixel may be able to use the low-band signal for uplink and the mid-band signal to augment its downlink.