Bad analysis, in this case.
The committee is partisan for the same reasons that any politically lopsided committee would be. If they were investigating parsnips and pomegranates it would be the same. Their interests, at least secondarily, are to undermine the other party.
As I say, judge the committee on the results. But don't try to claim it isn't partisan.
Charges of partisanship are irrelevent to the facts of the case. As long as factual events are the focus, and their potential to be taken up by the DoJ remains intact and credible, partisan or not, the legal repercussions matter, the work being done matters, and making the public aware of the facts as they reveal themselves matters. That said, as pointed out, Republicans had ample opportunity to be members of the committee, but most rejected the investigation itself as motivated solely by partisanship, not by events.
And for "good" reason: Seems
there was indeed a coordinated coup attempt. Rather important. More than an email scandal, it is a constitutional crisis and represents an existential threat to democracy, if one is to heed, oh, say, the majority of independent constitutional scholars and historians who have spoken on the matter. More importantly, however, is the hyper-partisan reaction to such factual revelations by the GOP, indicating that constitutional due diligence is not their thing anymore, Nixon being an object lesson in its political costs. Indeed, it goes deeper. The frequently heard strident claim that "the US is a republic" seems to be
pitchfork semantics* for "rightfully Republican", while threats to "democracy" are now welcomed as "sticking it to the Dems", language having been properly debased by design, "democracy" now being something only Democrats and other extremists, such as supporters of univeral suffrage, care about. What's important now, in effect, is to protect and continue the Trump-sullied SCOTUS attack on all rights not pertaining to White men.
*
Pitchfork semantics: Refers not to a shared common understanding, but to an alternate reality created out of whole cloth for the sole purpose of rebuttal, including the consequent inevitable contradictions inherent to ad-hoc reasoning. Relies on misuse of alternative definitions of same words in place of the most common definition, such as in the case of "socialism".