I don't think you can compare the Grasshopper curse to the Chainsaw Devil at all.
That cursed spirit was like narratively made out to be a stupid brawler and Yuji seemed to also have a hefty statistics advantage over him.
It's completely different from the way the Chainsaw Devil is portrayed as being a merciless, skilled executioner type character that destroys multiple highly skilled fighters easily.
There's also the fact that his limbs are shredding piercing weapons. They aren't like punches. When you throw a punch you can't really change the trajectory to try and sway it to a different target cause it loses a lot of power. With a chainsaw, you can move it anywhere and it's slashing through someone like butter.
If Yuji throws punches, he has to avoid the chainsaw moving towards his arms at all while he's attacking which is stupidly difficult especially when he has like DOUBLE the range. I understand he's probably got better skill but the gap isn't so much that he'd be able to overcome that advantage with "little difficultly." It is NOTHING like that grasshopper curse.
It wasn't made out to be a stupid brawler though? Nor did Yuji seem to have a hefty statistics advantage. It was stated that Yuji's skill far outclassed Ko-Guys skill, but he was presented as an actual threat that would employ sneaky tactics to win. It was even stated he had advantages such as a better "arm, jaw, and eyes" that are all better than humans. Itadori even noted that it wanted to keep the fight confined to close quarters since it had the ability to control all four arms independently of one another. Now, in
general knowledge/communication, it was more undeveloped compared to a normal human. And once Ko-Guy was defeated, Mahito stated:
"So Ko-Guy was defeated, huh? Looks like we have a skilled sorcerer on our hands."
Ko-Guy tries going for an execution attempt right after he failed to kill Itadori in hand to hand combat since he was out skilled so badly... Granted Ko-Guy definitely isn't as impressive as Chainsaw Devil feat-wise.
I agree Chainsaw are more difficult to deal with fists, but given Itadori is wary of weapons in general, he'd like just opt for dodging and redirects the swings of the blades that attempt to cut him. Worst case scenario, Itadori uses Cursed Energy to reinforce his body to minimize the cut as much as possible. He stated he didn't fear blades as long as he steels his body with Cursed Energy when fighting Yuta (But stated it wouldn't work against Yuta who could likewise imbue a shitload of Cursed Energy into Katana). Depending on the environment, he may also just scour the environment for a weapon/object to imbue with Cursed Energy to counter the saws.
The Grasshopper had far greater range (Was taller than Yuji even when crouched over) and four arms to likewise counter Yuji's two, but was completely unable to keep up in their clash even with better eyes. I don't think Chainsaw Devil can't tag him, but he'd have difficulty doing so. Yuji would likely wait for Chainsaw Devil to engage the battle to counter and evade the blades coming towards him, and if worse comes to worst, would be willing to sacrifice a limb in order to land a devastating blow (Such as a kick, headbutt, punch, etc.). Realistically, I think he'd opt for snapping the Chainsaws and then wailing on Chainsaw Devil. Then upon realizing he can regenerate, would aim for fatal blows, such as strikes to the head and heart.
(Btw, I'd note that you're equalizing their power systems so that Cursed Energy poison doesn't kill Chainsaw Devil).
