Can I use these interchangeably?

Our relationship isn't what it used to be.
Our relationship isn't the same as it was.
Our relationship isn't the same as it used to be.

Question

Can I use these interchangeably?

Our relationship isn't what it used to be.
Our relationship isn't the same as it was.
Our relationship isn't the same as it used to be.

Answer

All mean that the relationship has changed. However, '(something) isn't what it used to be' is generally used to mean that it is worse. The other two are neutral - the relationship is just different.

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