The "best" response doesn't objectively exist, but if it did, it would be a function of both time and quality.

For example, when you take 24 hours to respond, the message you're sending is that the person is a low priority, regardless of what text you've composed.

People who feel that anxious about composing the best reply should seek therapy to help them tolerate the distress of doing things imperfectly.

Perhaps composing the BEST response isn't the right tradeoff vs being available for your friends and not leaving them hanging?

A person I'm close to does this (takes days/weeks to respond to anything). Important as they are to me, I've basically written them off as someone I can rely on.

It takes years to compose the best response

Some perspective: sometimes the best response is signalling to people that they're important to you and that getting back to them quickly is important to you.

5 minutes might be too short, but the idea of waiting until you have time to fully respond makes sense.