It's been 5 years since the last time we've met. That's only my opinion 🙌 can someone correct me please 😂

If you want to emphasize that it was a long time then you should say: It’s been a long time since we last met (5 years ago). You can also say: It has been ( It’s been) five years since we last met. This one emphasizes how long it actually was. If it was that you met 5 years ago for the first time you just drop ‘last’ It’s been a long time since we met 5 years ago. In a spoken/ written language friends would usually say: We have not seen each other for the past 5 years! It’s been ages since we (last) saw each other/ met.