I don't think this responded to the original question. I believe I have the same issue as the original poster. Several (hundreds at least) times a day I want to open a given file on my local hard drive. I can either open a Finder window and navigate to it, or I can hit command-space, pop open a spotlight dialog, type part of the filename, and press enter as soon as the desired file appears in the results list. That process takes literally 2 seconds or less. With 27.2, Siri gets involved and takes upwards of 10 seconds to search the internet for how to locate a file that is right there in my documents folder. This morning, she was repeatedly unable to locate a file that existed exactly where I told her it was located.
You are correct that Finder / Spotlight index search (without Siri) is available within a finder window. But it is not nearly as convenient or accessible as the command-Space combination. The best I can do is:
Command-Tab to bring Finder to the front
Command-N to open a new Finder window
Command-F to enter the Spotlight search field / mode
type search string
Tab to get out of the search field
Arrow keys to navigate the desired result
Command-O to open the file.
Previously it was :
Command-Space
<search string>
Enter
I know Siri can do amazing things, but making basic things more complicated is literally going backwards.