Generally you know by year 5 of any tank exactly what you have, the problem is that you always hold out hope you have more:
1.All your young and good players become great (not just good)
2.All your prospects pan out
3.All your trades and signings pan out
Unfortunately if you don't have an amazing talent already and just a bunch of good talents, you'll be mired in mediocrity always hoping that the team is always 1 more development year of the current roster, 1 more top F/D/G away and 1 more good signing away from contending.
It's rough because you know if you trade those pieces they'll go on to have success, but simultaneously if it's not going to happen with you, who cares? In Toronto we saw that with Kessel, but if he had stayed he would've taken an awful team to an ok territory and maybe instead of Nylander/Marner/Matthews we end up with Ritchie, Provorov, PLD.
Honestly maybe we're overrating a lot of elements and underrating luck, Edmonton looked awful with all those 1sts, top picks, but when they got McDrai all of a sudden the same organization became amazing. Without top end talent I see a bunch of teams kind of stuck in perpetual mediocrity, i.e the Sabres, Sens, Wings where at times they look decent-good and you'd hate to trade away any of the players, but simultaneously if nothing massive changes like Colarado Mack all of a sudden living up to his potential (happened by year 5) and obviously drafting Makar, then you can't expect the teams to take the next step. And expecting that is obviously extremely unrealistic.
It's tough rebuilding a rebuild, but by year 5 you gotta get realistic with what you have because IMO being stuck as a decent-good team with no chance of winning the cup is worse than a perpetual rebuild, at least in theory the perpetual rebuild can right itself (i.e Edmonton), but being decent-good is even worse.