Your question doesn't really make sense.
Given the information available at the time, I think the same as I thought then, that it was the right thing to do. Obviously now we see how it has panned out, I wish we'd sold for, say, £100m (if anyone would pay it). But that doesn't mean my original thinking was wrong - just that it panned out differently. That happens all the time - for example, when Leicester won the league, I presumably wished on the last day of the season that I had bet my house on them doing so at the start of that season. But it would have been a very foolish bet based on the information available at the time and the probability of it happening. Similarly with Kane, if I knew his performances would fall off a cliff then I probably would have taken the money - but all the info we had in the summer - including what we had seen of Kane as a professional over several years, and our experiences of our previous top players' performances after being 'forced' to stay one last season - suggested that Kane would continue to perform well, maybe even better to prove to Pep how much he is worth ready for the next window.
So yes i do still think it was the right thing to do at the time, but equally I recognise that it panned out differently to how it could reasonably be expected to have done.
By the way, personally I'm not convinced yet that all is necessarily lost with Kane - sometimes players do recover their 'mojo' for whatever reason. The only way I can see out of this is for Levy to sit down with Kane, and give him a written agreement that if he achieves certain targets this season, then he can leave for (say) £100m next summer. That would save face to some extent for Levy, bring some money in, get Kane trying again, and give the player light at the end of the tunnel in respect of his transfer desire.