It wasn't always peak Moss/Welker or peak Gronknandez but most seasons he had weapons that he was good with:
Brown/Branch/Givens
Moss/Welker
Gronknandez
Gronk/Jules/dola
I'd say arguably the replacement with weapons for the offense was sufficient until 2018.
2006 was terrible after Branch was traded, but the next offseason Belichick went out and traded for Moss (who got a top-end extension the following season) and Welker (who cost a 2nd and 7th to a division rival).
In 2010 when Moss was gradually declining they drafted Gronk and Hernandez. After Moss got traded in 2010 they got back Branch who had productive 1.5 seasons alongside Welker and the TEs.
In 2012 they got another close to 1000-yard receiver in Brandon Lloyd to team up with Welker, Moss and Hernandez.
2013 was a (relative) down year after Welker left, but still, the receiving corps would have been sufficient if Hernandez hadn't gone criminal.
And between 2014 and 2017 the combination of Gronk, Edelman, Amendola and whoever was the fourth receiving option - be it LaFell or Hogan - was capable of keeping up with the best.
Yes, they didn't have an all-pro WR after Moss and Welker - but why would you need that if you have Gronk and Edelman already? You don't go to 4 Super Bowls in 5 seasons with weapons that suck. It wasn't until Gronk started to slow down that the weapons started to degrade and Belichick did mess up the 2019 draft by going with N'Keal Harry rather than Deebo Samuel and AJ Brown after losing Gronk, but until then the weapons were top third of the league if you look beyond just WR.
I've said to posters on here that had AB kept it together in 2019 we win another superbowl. The offense is what kept us back thst season.
I still recall the media reactions after Brown was signed - it was in consensus to the tune of the rich get richer and the Patriots are again favourites to win it all. Brown was signed after a 33-3 shellacking of the Steelers in which the offense put up 465 yards with Edelman having 83 yards receiving, Dorsett 95 and Josh Gordon 73.