Exactly. There were still poor sides around, they were just different to now.
Take Bobby Charlton for example. Scored 3 against USA in an 8-0 win, 3 against Luxemborg in a 9-0 win, 3 against Mexico in an 8-0 win, 3 against Switzerland in an 8-1 win. Add in home internationals every season.
Not to downplay Bobby Charlton's acheivements, because you can only score against the opposition you play, but there do seem a lot of people trying to denigrate Harry Kane.