So the question here isn't so much about the change in power now as it is in the change in power over time. That change doesn't clearly favor Democrats or Republicans. Rather, it favors majorities over minorities. And a corrective on that front has been overdue for decades. The only thing worse than a Senate where the majority has the power to govern is one where it doesn't.I'm going to keep banging this one in, because it's terribly important. Removing the filibuster doesn't favor "majorities." It favors one particular majority. Not a policy majority. The party majority.
Remember, nominations that the majority party in the Senate opposes won't necessarily make it to the Senate floor in the first place, even if they would actually win if they came to a vote. Indeed, one can imagine a House-like Senate refusing to bring nominees up for a vote unless a majority of the majority party favors it.
"Majorities"? There's a majority right now for ENDA in the House, most observers believe. There's almost certainly a majority for a Senate-like immigration bill. I suppose it's even possible that there's a majority in the House for some very mild gun legislation. But in a body in which the majority party runs things, those other majorities aren't getting votes.
The thing is that there are multiple majorities on multiple issues at any one time in any legislative chamber. What parties do is structure things so that certain majorities are allowed to express themselves -- and others are suppressed (meaning that in those cases, the minority wins). That's fine; in fact, it's better than fine, since legislatures probably couldn't function very well without that kind of structure. But there's no reason to assume that the party majority is the only majority that matters, or that it's always inherently better (and more democratic) to allow the party to determine which majorities count.
And that's without getting into the more complex question of whether majorities should always win in a democracy. I'm strongly convinced they shouldn't (a classic example is when an indifferent majority is opposed by an intense minority). But put that aside. Again: reforms which favor party leadership simply do not favor chamber majorities in all cases, at any rate. They favor the majority party.
Strict majority party rule is, to be sure, better than strict minority party rule. Or, even worse, the incredibly bizarre situation in which a minority of the minority party intimidates the bulk of that party into doing whatever they say, and then abuses chamber rules to dictate to the majority party some policy which in fact only a slim majority support. So, yes, given the situation, Harry Reid and the Democrats had no choice but to act, and the result is in fact better than what they were faced with. To say that it necessarily empowers majorities, however, is another question altogether.