English has no future.

As I undertand the point, (1) there are many uses of modal constructions with will, only some of which entail futurity.

(2) There are many ways to express futurity in English, only one of which is the modal construction with will.

So it is arbitrary to take the cases where (1) and (2) overlap and call those the "future tense" in English. You might as well call some other construction the future tense--the periphrastic "going to..." construction for example.

Compare to Spanish: there is a dedicated verbal form for the future. This form can also be used for other, non-futurity cases:

Tendrá sueño might mean "she is probably sleepy," rather than "she will be sleepy." It is also used as an imperative, as the English will is.

There are also a periphrastic form for future events: Te voy a matar, and other ways of expressing futurity which don't involve the dedicated verb form. So is there a future in Spanish? Is it arbitrary to call that verb form the future, when it can be used for other things, and other forms can be used in place of it? The fact that it is a morphologically distinct tense is the decisive factor here, I think.