You should provide some context; even better the whole sentence that you try to convey from English in French. See

https://www.linguee.fr/anglais-francais/traduction/only+suitable+for.html

For instance:

The problem is that these techniques are only suitable for a qualitative description.

Le problème est que ces techniques ne conviennent que pour une description qualitative.

Ne…que (no negation!), uniquement and seulement can be interchangeably used in most cases. But for conveying if only/not only one must use seulement.

Je n’aime que la viande/J’aime seulement la viande/J’aime uniquement la viande.

both convey

I only like meat

But

Si seulement j’avais mon portable!

conveys

If only I had my mobile!

and

Non seulement elle est arrivée en retard, mais elle voulait aussi parler en premier.

conveys

Not only did she arrive late, she also wanted to speak first.

So in your case, I would say that the turns

Le problème est que ces techniques ne conviennent que…

Le problème est que ces techniques sont seulement/uniquement adaptées à…

and so on, are equivalent. Uniquement appears to my not native ears stronger and more formal though.