I've been out since 2003 (and started this adventure as an FDNY Auxiliary in 1968). The most obvious changes are bunker gear, enclosed cabs (and assigned seating), radios, power tools, improved SCBA and tower ladders/elevating platforms. I got to tell you though, I miss hanging on the side of a rig, wind in my face, pulling up my boots.
As the years wore on Rapid Intervention was introduced; better accountability systems came about; training became more focused, frequent and intense; our role was expanded to include EMS functions, Haz-Mat operations and terrorist/terrorism response. Texas A & M has a great training facility in College Station for fires and emergencies. Been there many times and always came home with new tricks.
What I've seen since I retired, particularly out here in the Pacific Northwest, is an increased emphasis on defensive/exterior operations. The aggressive interior attack, long the hallmark of fire departments, has been replaced, at least out here, by a hit it from the outside approach even when there is a possible life hazard (this is certainly NOT the case back East), so many times a news story will report on a fire and when interviewed a "PIO" will say the building was too hot to enter or there was too much fire.
Some things will never change, thank God. The camraderie of the troops, the dedication to the job and the ability to overcome whatever BS "city hall" throws our way are prime examples of an enduring spirit.