Where you have shading, yes — meaningfully. Optimisers shine when any individual panel on a string is shaded at some point in the day, because without them a single shaded panel drags down the whole series-wired string. Measurements show that even very minor shading on one panel can have a large impact on output, so isolating that panel with an optimiser recovers production you'd otherwise lose. They're also useful when you mix orientations on a string (say south and west panels together).
Where they don't earn their keep is on a clean, unshaded, single-orientation roof. If nothing ever shades your panels and they all face the same way, optimisers add cost without much benefit, and it's fair to say so — they're a targeted fix for shading and mismatch, not a blanket performance upgrade. So the question isn't "are optimisers good?" but "do I have shading or mixed orientations that justify them?" Many people sensibly fit them only on the specific panels that need them (for example the few that a neighbour's tree shades in winter) rather than the whole array.
If you're unsure whether shading will be an issue, walk the sun path across your roof through the day and across seasons — winter's low sun casts long shadows that summer doesn't. Panels affected at any point are candidates for optimisers; panels in clear sun all day aren't. It's a per-panel, situation-specific decision, and spending on optimisers where there's genuinely no shade is money you'd be better off keeping.