That's very different. A simple potentiometer is not going to have the performance of A90. Not even close. You get a trade off between, channel imbalance, channel crosstalk, output impedance, input impedance (loading previous stage). Operation is very different too. You can get a dedicated preamp that's for sure. But it's nothing like a pot.
Similarly, when I mean switch I didn't mean a component switch but an actual switcher with chassis and everything. It's way cheaper than A90 and does the job. You can get some of those like A B switch, splitter. They are designed to do the very same thing. There's no meaningful measurable difference between switches. But preamps can be very different.
Plus you can use the preamp to control the volume regardless of whether the following stage having volume control or not. It's a much superior preamp is majority of preamps on the market.