When high-quality FTSE shares lose close to 40% of their value in 12 months, my ears prick up. Because in my experience, the best buying opportunities are often found among the stocks that have fallen the hardest, especially when the underlying business is still intact.

Right now, two dominant UK platforms are sitting in exactly that position: Rightmove (LSE:RMV) and Autotrader (LSE:AUTO). And the losses have been painful.

A £1,000 investment in Rightmove in April last year is now worth around £604.30. Meanwhile, the same investment in Autotrader now stands at a similar £617.10.

What on earth happened?

What went wrong?

For Rightmove, the trigger was a single announcement in November 2025. Management revealed it expected 2026 underlying operating profit will grow by just 3%-5%. That significantly missed analyst expectations, driven by the surprise announcement of a £60m multi-year artificial intelligence (AI) investment programme.

The guidance cut triggered the worst single-day crash the stock had seen in years. And since then, with the emergence of a £1.5bn class action lawsuit alleging abusive pricing practices, the shares have continued to tumble.

Autotrader’s situation is slightly different, driven primarily by a lack of supply. The pandemic was six years ago, yet there are still several lingering headaches that continue to plague the second-hand car market.

Pandemic-era production shortfalls significantly reduced the number of new cars entering the second-hand market today. Yet demand remains strong. As such, the relatively few cars getting listed on Autotrader’s platform are being sold unusually quickly, often within a few days, even when listings aren’t being promoted with the premium advertising packages Autotrader sells.

This impact has been further compounded by a botched rollout of its new Deal Builder tool, which triggered subscription downgrades and even some cancellations.

Is there a recovery play here?

Despite the painful share price drops, the bull case for both businesses remains quite promising.

Rightmove controls the UK property listings market with a near-monopoly grip and a staggering 70% operating margin. Revenue still grew 9% last year. And while the AI investment is painful now, the company projects it will pave the way to double-digit growth by 2030, backed by an even stronger competitive moat.

Autotrader’s equally formidable, commanding over 75% of the UK’s online car market. And the used car supply crunch driving today’s weakness is cyclical, not structural, in my opinion. So as interest rates steadily drop and supply chains eventually normalise, the pricing power of its platform should eventually start roaring back.

That said, the near-term picture does remain murky. Rightmove’s near-term earnings will remain pressured by AI spending that isn’t guaranteed to deliver success. And there’s no denying that the ongoing class action adds real legal uncertainty.

For Autotrader, the limited second-hand car supply is so far showing few signs of being resolved any time soon. And the landscape’s now looking even more precarious as higher energy prices apply even more pressure to the automotive sector.

Nevertheless, with both businesses generating exceptional cash flows, holding dominant market positions, and sitting at multi-year valuation lows, I think this is exactly the kind of FTSE shares crash that long-term investors shouldn’t ignore.

Obviously, not every fallen stock deserves a second look, but these are definitely two I’m seriously considering.