Learn Hardcore Chinese: zhèxiē shícái gòu le.

Because 够 here works like a state word/adjective meaning "to be enough", and in Mandarin, words of this type can act as the predicate without 是.

So:

这些食材够了 = These ingredients are enough
literally: These ingredients enough now

Using 是 here would sound unnatural. This is similar to:

菜好了 = The dish is ready.
钱够了 = The money is enough.

So Chinese often does not need a separate verb like English is/are in this kind of sentence.

What does the 了 mean here?

The 了 here is the sentence-final 了, which often shows a new situation or change of state.

So 这些食材够了 does not just mean these ingredients are enough in an abstract sense. It often suggests:

Now they’re enough
We have enough ingredients now
After checking/adding some, it turns out this is enough

Without 了:

这些食材够 sounds incomplete or unnatural in most everyday situations.

With 了:

it sounds natural and complete.

Also, this 了 is not simply a past tense marker. It does not mean the sentence is in the past. It marks a change in the situation.