"Reagan negotiated a massive change with Gorbachev" from a position of strength, and with resolve, and achieved important aims, regardless of ex post facto quibbles which ignore the gravity and urgency of the time.
The more accurate characterization above is also, unfortunately, not the character of current U.S. foreign policy. This statement is far more influential to our present state than any legacy considerations of strategic shortsightedness on Reagan's part. He expected we would build from the foundation he laid down, and we haven't.
(edit for typo)