I never doubted that. But even in "skill of craft", Fëanor was (almost) one-dimensional: a smith. You might object that Fëanor did more than just create jewels (and don't forget that he was the first Elf in Aman to create weapons!), that he also contributed vastly to what we might call Elven "philology" (something that would make him sympathetic to JRRT). To that I reply with a term I have heard coined for JRRT in real life, a "word-smith", here clearly meant in the fine-arts version of gold- or silversmith. But I utterly refuse to limit a definition of Elven greatness to the very narrow field of Fëanor's positive traits (and is forging weapons in Aman positive?) while ignoring the vastly greater field of his deficits.
Leadership? Here Galadriel is better even at the rebellion of the Noldor, and that grows to orders of magnitude over time. Fëanor was a total failure as a leader. Leadership does not consist of bellowing "Charge!" and then doing so blindly. What Fëanor did with his utterly brain-dead oath. Or, as you have posted speculatively (if I could just find the thread - meh!), that had Fëanor just waited for his seven sons and not charged in a blind fury to the gates of Angband as described in the published Silmarillion, chapter 13 (oops?) of the Quenta section, "Of the Return of the Noldor", things might have been different? I doubt it very seriously. As JRRT wrote it - and you mention of "fire of heart" above seems to me to go in the same direction - such rational considerations were apparently not something Fëanor was capable of. His mortal (properly Hröa-destroying) wounding before the gates of Angband was practically inevitable.
As per JRRT's concept of him, yes. But the following passage in the published Sil sums up Fëanor for me irrevocably:
"And looking out from the slopes of Ered Wethrin with his last sight he beheld far off the peaks of Thangorodrim, mightiest of the towers of Middle-earth, and knew with the foreknowledge of death that no power of the Noldor would ever overthrow them; but he cursed the name of Morgoth thrice, and laid it upon his sons to hold to their oath, and to avenge their father."
Excuse me? This is scorched-earth in its purest form. I assume that I do not need to tell you which rabid human lunatics did likewise, including a very current one. Whatever Fëanor's creation of the three Silmarils may have achieved artistically, they were not just ambivalent in Middle-earth, they led to destruction that relatively exceeded the 20th century's two world wars. Fëanor defines unbridled arrogance to me just short of the ultimate nihilist Melkor.