Hi Portana,
I'm only a month into all of this, so I can't give great reassurance regarding what you're going through. I can tell you, the people above that have responded to you, are the ones I get advice from the most about my sugarcat.
Take a look at my spreadsheet, Fanby varies almost every day. We are making progress, but without testing I wouldn't actually be able to see that.
My first vet who diagnosed Fabby sent me here to learn about diabetic cat food. (I had already found this site, but it was reassuring my doc sent me here.)
The first vet is quite expensive, so I found a 2nd vet that is non-profit. I showed her our spreadsheet, and she was able to look over the numbers and be very happy and confident with Fabby's progress. I test Fabby 4x a day. So, while I can't guess at what your vets motives and experience is, I can tell you diabetic treatment for cats varies with many vets. It seems almost subjective.
With my own healthcare, as with my cat's care, whatever I'm doing must make sense to me, or I'm just not going to do it. My diabetic Grandma would never shoot insulin without testing, so I'm not going to either.
Since your the one managing the care of your loved one, make sure your treatment advice makes sense. Maybe call up and talk to your vet about your concerns (try to avoid saying The internet says", as medical professionals tend to check out if you say that). Or check around for a 2nd opinion.
For me, I need my medical team to be on the same page with me working toward a common goal, so I don't envy the spot you're in.
What it really comes down to is what you believe is best for your kitty, since you provide the care.