Would switching to full frame Canon and getting that lens be an upgrade over my Fujifilm gear?
For some shooters it would be. For others it would not. For a true photographer it shouldn’t make a ton of difference either way. They’ll do good work with either. One system may make doing that work easier than the other, but the work you are describing can be done perfectly well with either set of tools mentioned in the question above.
Please take note, I used the word ‘photographer’ above, not the word ‘professional’! ‘Professional’ just means you’re getting paid. It says very little about the quality of your work and a lot more about your business, marketing, and social skills.
Charles W. Leadbeater said, ““It is one of the commonest of our mistakes to consider that the limit of our power of perception is also the limit of all that there is to perceive.”
The problem with some folks is that they are so limited that they assume everyone else has the same limitations that they do. They also assume that their way of doing photography is the only way, and that the type of photos they take are the only types of photos worth shooting. Since one of the basic rules here is that we’re supposed to be nice, I won’t say any more about the person who, unsolicited, advised you to dump your current setup that is working perfectly fine for you in order to start using what he apparently needs to validate in his own mind as the best way to go about it.
Now, about gear.
While it is true that better gear won’t make you a better photographer, it is equally true that any photographer is limited by the capabilities of the gear being used.
There’s an old saying that has been around photography for a very long time:
Gear doesn’t matter.
It’s certainly true, but it is only half the truth. The rest of the truth is this:
Gear doesn’t matter – until it does.
When the technical capabilities of your gear are not up to the task for the shots you want to capture, then and only then will the gear matter.
When your gear does matter, you’ll know. It will matter because the gear you are using will limit you from doing work that you wish to do and that you have the skill and knowledge to pull off. Until you reach that point, the gear you are currently using is perfectly fine for you.
For more, please see: When should I upgrade my camera body? The answer there is just as equally applicable to lenses or entire systems.
What features would cause a portrait photographer to choose a DSLR over Mirrorless?
Should I buy a new DSLR or spend the money on a photography course with my point & shoot?
Will I see enough improvement moving from EF-S to “L” lenses to warrant the cost?
How does focal length relate to macro magnification?
the best way to improve image sharpness on Canon 700D