It's not a "Disney" decision, it's just the timing of things. I'm not giant Disney fan, but we have to stop saying every detail we don't like was a conscious decision made by the ghost of Walt Disney to hurt us.
That said-- you're not wrong at all about the sabers. This is purely due to the stunt blades now being able to be lit. From ESB to TFA they were animating over narrow stunt blades. In ANH we had the scotchlite tubes, which as we know, required light contact. AOTC, ROTS and TFA all did close ups with lit blades for effect lighting and reflectiond. But starting with TLJ, they began dueling with lit stunt blades. Now instead of animating over thin rod, they have to cover a 1" practical glowing rod. So you have the thickness AND the fact there is real light on top of the animated glow. It defintely makes for thiccsabers.