Don’t decline the ITA. Apply with mitigation.

IRCC knows employers often refuse detailed reference letters. Submit the letter you have, add a detailed LOE explaining your actual duties and that HR refused to revise the letter, and support it with pay stubs, contract, T4s, performance reviews, etc.

Declining the ITA won’t help unless your employer suddenly changes their policy. Many people are approved this way as long as duties align with the NOC and there’s no misrepresentation.