It seems to me like there's some straw-man arguments being made by what, for the sake of brevity, I'll call the anti-Eriksen crowd.
The first is that those who think Eriksen is a very good player (one of the best on the team) and difficult to replace also think he is THE best player on the team or one of the best players in the world. Maybe some people think that. I know I don't think that.
The second is that those who think Eriksen is a very good player are all saying "the stats, the stats!" to defend Eriksen's performance last season. Maybe some people are doing that. I know I'm not. The stats from Whoscored suggest that Eriksen's performance in the Premier League (a 7.08 average) was down significantly from the year before (7.4), the year before that (7.53), and the year before that (7.45). But a 7.08 is still quite good. So the stats might suggest that Eriksen went from very good/verging on excellent to just good/very good last season. An off-season, but still a very effective player.
Christian Eriksen - History
When I pointed out that Eriksen had 6 strong seasons at Spurs and couldn't believe the slagging he was taking, I was then told that it's only last season that was being slagged. This part is especially incredible to me. The anti-Eriksen squad is now suggesting Eriksen is not that good and is fairly easily replaced because he had one modestly off season? If he was 32, I'd get it. You could argue he's in decline and this is just the beginning. Or if he'd picked up a chronic injury last season that will limit his production forever. Or if we'd gotten a new player that had forced Eriksen into a position he's uncomfortable with, and Eriksen would have to keep playing in that position, then I think you'd have a reasonable argument for just using Eriksen's most recent numbers. But none of that is true. Eriksen is 27. He's in his prime. He's healthy. The way we play, and the way we use him has been largely consistent during Poch's regime and will remain so in the future. He's far more likely to return to his historical average than not. To ignore 5 years worth of performances in favor of the single most recent year is absurd.
I don't know how ANYBODY could think Eriksen will be easy to replace if he leaves. It should be obvious (but somehow isn't) that he's one of our best players, AND that we don't have anybody else who can do what he does as effectively as he does it. It honestly seems like the anti-Eriksen crowd is trolling, but somehow I think they really believe what they're saying.
So here's where we stand with Eriksen:
1) He's a very good player, one of the top players on the team, and has a unique skill set that will be very difficult to replace. But he's not the best on the team and not one of the best in the world.
2) He had a modestly off season last year, but was still good.
3) He's more likely to return to his long-term very good/verging on excellent performance level than repeat last season's performance level.