There in Matthew 18 the quotation or verse (verse 18) which you bring was not addressed to Peter specifically or alone, for Christ is seen there to be speaking to them all directly, corporately together, all of them at once, having rather also disestablished at that point (prior to verse 19, also!) that "the church" be Peter alone despite what can be said as to his "rocky-ness" even if WE here in discussion be limiting that (alone) consideration to discussion of authority flowing from or through Peter (alone) to each of the rest of the assembled disciples.
This was much more the original and earliest sense of the church -- as to how the binding and loosening spoken of would function.
Claims to there having been established a singular papacy, one over all the rest --- did not arise until centuries later, taking many more centuries to more fully develop (in the minds of some, with it developing in the minds of those of Rome -- but not much elsewhere).
Effort to make excuse for having done so (not that either of you which I address this reply here on this thread have done so) by pointing towards what conciliatory elements there can be found within papal system, still ignores such as verses 16 & 17 in that same chapter, and very much verse 19, for by the sense which can be gathered from the chapter more widely --- Rome alone (successors there) was never in earliest times "the church" alone (or the singular "rock" alone) or considered having the one bishopric to which all others must unilaterally yield, or else chapter 18 of the Gospel of Matthew becomes distorted if not undone.
Can you see it? It can be found (in addition to elsewhere in scripture) in the earliest writings of church note-worthies (Early Church Fathers, as Schaff and others referred to those) -- with many times in those places when Peter alone is being spoken of, it not be in additional context of Peter alone having been authorized with the same binding and loosening, as is found in the very chapter which you have pointed towards. Yet rather; when those ECF's wrote of Peter, it was as his being or serving as example of what the church universally held, with this again -- not contemplated that those powers of true spiritual authority to then being funneled singularly through successor's of one "church office" of bishopric, more than or ABOVE all others.
Well like Luke the author of Acts for some strange Holy Spirit moment in scripture just has to write down the verses on if its of God it will not be stopped as prophecies by the Famous Rabbi in acts. The Catholic church is going for Two thousand years. Peace in Christ.