The group game between Belgium & England hardly tells the story. Belg back-ups beat England back-ups in a close game; but that hardly exposes the gap between two sides.
That day ENG started with -
Pickford, Jones, Stones, Cahill, TAA, Cheek, Dier, Delph, Rose, Rashford & Verdy
While Belgium started with -
Courtois, Vermalen, Boyata, Dendonker, Dembele, Fellaini, Throgan Hazard, Chadli, Telemens, Batsuayi, Januzaj
Difference is, this England team doesn't have that outstanding individual (s), that Belgium has - Southgate got the best out of his average squad playing collectively good soccer; but you replace any player in that XI including Kane, it hardly makes better. Does it really make much difference, if I replace Jones & Cahill with Walker & Maguire? Or Tripper, Henderson, Young, Ali, Sterling, Kane for the starters?.
Compared to that, Belgium has few individuals, who are far better in skill - their ceiling is much higher. Replace Belgium starters (where applicable) with Kompany, Alderwield, Vetronghen, Munier, Hazard (Eden), KDB, Carrassco, Witsel, Mertens & Lukaku .........
These days, International soccer is too close - 2-0 actually is a domination, 3-0 is rout; game has moved from the fantasy days where you can dream of putting ball to Pele's foot and he'll dribble past 12 players to score

........teams (even Asians) are far more tactical, compact and organized - Korea kept desperate Germany at bay for 90 minutes at then hit back on break; therefore for such a low stake game, any prediction is risky. But, in a 4231 formation, you ask me, 2 England players will start for my combined team - Kiren Tripper, that too because he scored a goal, on sure soccer merit, he doesn't come ahead of Munier at RB, and Kane because he is going to win the softest Golden Boot ever (& Lukaku had a poor game in SF)
1 Courtois
4 Tripper, Kompany, Alderweild, Vetrongen
2 Witsel, Chadli
3 Mertens, KDB, Hazard
1 Kane
It's not even a remote contest - but it's the most useless game of a WC, so anything can happen on the day.