As mentioned, you can copy the Color Books from the Presets>Swatches folder of a previous installation into the Ai 2023 Swatches folder.
In the end I signed up to Pantone Connect because there are hundreds of new colours missing from the old Pantone color books. Those haven't been updated in years and I welcome a solution that keeps the swatch books updated, but the pricing is insane.
My biggest issue is the Pantone Connect interface in Illustrator. The window is huge, almost double the width of the other panels. Fine on a 27" screen but a complete pita when working an a MacBook. There is no reason for it to be so large and it only displays 2 PMS colours side by side on it's smallest setting. Also the process of choosing a color and applying it to your document is a complete joke.
As with the old swatch panel, you can search for a PMS code, then you just click the swatch to apply the spot colour to your artwork right? Wrong! If you click the swatch, it applies the CMYK equivalent to your artwork. To apply the PMS color, first you have to click in the corner, add to the document swatches, then find and click the color in the document swatch panel (another swatch panel that takes up screen space). So what was a 3 second process, now takes 15-20 seconds.
They also need to fix the order it displays the PMS colours. For example, if you search '425', it displays 425 C at the bottom of the list, so you have to scroll down past every other PMS color that begins with 425 (4250, 4251, 4252 etc.) before you get to the colour you actually searched for. That adds another 10 seconds to what was previously a simple process.
Overall in terms of usability its a huge step backwards. I really hope they spend some of the extortionate subscription fee to develop the plugin properly.