Man the knees are jerking hard.
All of the top sides are developing; none are gun standout teams. You'll get games where they look awesome, and you'll get games where they look utterly inept. We're in a weird era of international cricket where teams are, overall, pretty evenly matched -- but because they win by shedloads and lose by shedloads, not because every single game is going down to the wire.
Sometimes perfectly fine teams play poorly. That happened to South Africa early in the series, and it happened to England in this game. Equally, sometimes perfectly fine teams play extremely well (invert the end of the last sentence). No reason to be so incredibly reactionary that you throw out babies with the bathwater.
ABdV failing a couple of times doesn't mean he can't handle the captaincy; he's been perfectly fine doing it in the shorter formats. Maybe he, uhh, just had a bad day at the office, got a good ball, or made a mistake. He's not Superman, and he's not Bradman either. **** happens; after three innings you don't have nearly enough to draw extended conclusions. Similarly, as bad as he's been in the last year, I think it's a mistake to write off Faf as done for good. The guy still averages over 40 in Test cricket, made 86 in Cape Town, and has played some pretty bloody important knocks for South Africa in recent years. He sucked in India and was pretty mediocre here, but to condemn him as a Test cricketer is stupid.
Similarly, one quick ton for Quinton de Kock doesn't mean he's suddenly an amazing Test batsman. He's good, but he has a lot to learn (and I imagine he will).
On the England side, writing off Compton and Taylor to immediately go back to Ian 'Pretty cover drive but averaging 3 in the last year' Bell after a single loss is similarly stupid. Compton has been perfectly fine this series, though he does certainly need to kick on and make the place his own (hey Bayliss, help him out there, hey?). Taylor deserves more than a handful of Tests to prove himself. He's done it at FC level, and he's done it in ODIs. Give him a proper chance to adjust to Test cricket.
As for the opener? Who knows who'll do that for the home summer. I'm gonna say Cook-Compo and bring in Ansari at 3 because Ansari
, or give Tom Abell a very premature crack because Somerset, but, uhh, yeah. I'm willing to concede doom and gloom there.