Well, it can still be useful for many things.

You can see if a flight has no seats left, limited seats in cheap fare buckets (book quickly!), or is wide-open. You may want to choose a flight (closer to the date) that has loads of availability in Y, so you've got a good chance of an empty seat next to you. Or you may be a top-tier élite, and want to go for one that almost booked-out in Y, but half-empty in C/J, to go for that op-up, or have a better chance for an MFU.

And, of course, not all TAs and airline websites offer the same fares. Perhaps you see a price of £500, but you can see full availability in many fare buckets, prompting you to widen your search.

If you're doing a complex, multi-leg search, it can help to find that one sector that bumps your fare right up to full-fare, and find out the alternatives.

It can be a very useful tool.

(Or you could have a wonderful TA, who does all this for you. I don't, sadly...)