Vintage Thorens turntable -Good or Bad?

Can't speak to the 126 but I bought a 166mk II and it plays and sounds great. It is in excellent condition and shows little sign of wear or usage. I did put a new belt on it and bought a cartridge for it. As to whether yours is worth it or not I guess it depends on how much you paid for it and what condition it is in.

How much you paid for it certainly has everything to do with the answer to your question. Unless you paid too much, or something is wrong with it, you are not wasting your money. The TD126 was a fine sounding table in its day, and you would probably have to pay a lot more than you have in it for better today. It is certainly worthy of a decent cartridge.
A high-end shop may not be interested in an old Thorens, but I think you might be surprised how good it sounds. If the bearing never dried out, and everything works, it may be worth upgrading. Tonearm wire/cables, maybe tonearm/armboard.

It's a good deck.

If it has the stock Thorens tonearm (TP16 MkII) it requires a high compliance/compliant cartridge, due to the lower mass (<8 grams I think).

When setting it up look into redamping the springs as the foam sponges (located inside the spring coils) break down with time.

I used wedge shaped makeup sponges in my TD125, but research what others are using for replacement parts.

Maybe someone was having a bad day @ Brooks?