Man Utd do not need money so wouldn't sell De Gea. Also Kane is in a different league to what Countinho ever was. Countinho's price was super inflated due to the Neymar saga and liverpool got a fantastic price. There is no doubting that Liverpool are a far better rounded team with him gone than if he had stayed. You would have never had the money to buy VVD and Alison if you hadn't of sold him so what would you of rather had?
Quickly on the Utd and Spurs points. Utd don't need money yet they refused to pay the price to get certain players in the last 2 summers and as for Kane being in a different league I think that's mad too. Coutinho was without doubt our best player in the 18 months prior to leaving (he was better than both Salah and KdB in the first half of last season) and as good as any player in the league. Maybe Utd did have the money for x but decided he wasn't worth paying the extra £10m but I'd hazard a guess that Liverpool wouldn't have ordinarily paid £60m on Allison (his fee also inflated due to Coutinho's sale) either but were willing to pay an extra £10-15m above what they were comfortable with because of such a large fee received. Maybe had Utd sold De Gea then they'd have paid an extra £10-15m on Perisic and Maguire than they thought they were worth.
There's so many assumptions in your post. Why wouldn't have Liverpool signed VVD if he stayed? You do realise that we had VVD lined up around March time, long before there was any possibility of Coutinho leaving? As I said previously, had Liverpool got VVD and Keita the summer before last then I think we wouldn't have signed Ox for £35m and instead would have waited to get him on a free last summer. We also wouldn't have been in the market for Fekir at £55m who we didn't sign nor sign an alternative to (so you'd assume that money's still available). If Coutinho was still at the club we're probably not signing Shaqiri either. Suddenly Coutinho's sale hasn't effected the signing of VVD or Allison at all and both those signings would have been for reduced fees too.
When Spurs sold Bale everybody was wetting themselves with all these football manager names that they were signing to replace him. It turned out that football manager is a lot easier than the real thing though and Spurs really struggled to even stand still let alone move forwards for a couple of years. Same story when Liverpool lost Suarez and god knows how many other times in the past a club has sold a star player.
I'm sorry but to say losing your best player is a blessing is simply bonkers. As I said, it's whatever you make of it. If you're smart with the money you receive then you can be better off but if you're not smart with the money you're just as likely to be worse off. The way Liverpool have dealt in the transfer market over the last few years I have little doubt that our side, although different in terms of players and maybe balance, would have been equally strong overall as we are now.