Of course it's not an all or nothing, but IMO it is very situational dependent.
If the court was currently, say...6 to 3 or 7 to 2 "conservative" to "liberal", then one person would clearly not be a big factor. Since the current court is generally thought to be 5 to 4, that one person now becomes very important to the point where outcomes are now liable to swing the other direction. 2nd Amendment rights, right to life/abortion cases, property rights (etc) would then be subject to the ideology of the left from the judiciary perspective.
A leftist judiciary, coupled with a leftist Congress and a leftist Executive branch is clearly alarming. Not to mention, a leftist media and leftist education system. At least, as of now, one branch isn't beholden to the socialist/progressive ideology, a branch which isn't subject to elections every 2 to 6 years.
It isn't. It is 4 to 4, with one flipping coin in the middle. There are 4 fairly reliable conservative constructionist justices. There are 4 very reliable hard-left liberal activist justices who see the court as an instrument for implementing changes that cannot be won at the ballot box, and view the constitution as malleable. Then there is Kennedy, a "maverick" if you will, who sometimes sides with the leftist and sometimes sides with the Constitution. What he uses as his guidepost is ANYBODY'S guess.