I think the legacy of this tournament's performance will only be decided when we see if this is the start of a team setup that can continue to challenge, or a one-off.
On the one hand it's hard to make a technical case that this is an excellent team based on narrow victories over Tunisia and Colombia, comfortable beatings of Sweden and Panama, and losses against Belgium and Croatia. The team was competent, well drilled rather than excellent, and in a tournament where the draw favoured England, that was enough to take them to the semi-final.
On the other hand, competent is a big step up from a lot of what we've seen in past tournaments, and ultimately you get trophies for winning games, not playing exciting football. There's no overlooking the fact they've achieved what England's only achieved twice before and what (checks wikipedia) 207 other countries would have loved to have taken off their hands.
I can easily see a situation where England in the semis of this World Cup becomes a "remember when" in the way that Wales getting to the last four of Euro 16 must already be for them. But I can also see it being the start of something bigger, and wiping out the negativity around the England team could be a big part of that. I think tomorrow's game could actually be a bit of an indicator - get pasted by the Belgians and it'll rub in the hard facts of what they've achieved. Get a win and it'll start the firing gun to roar into a strong 2020 Euros campaign.