When have the Patriots under Belichick ever had a true #1 WR? Obviously, it depends on how you define that, but I usually think of a game-breaker type who puts up major production (not just a fast WR who doesn't actually catch many passes). So clearly Randy Moss was a true #1, but he only played for NE for three full seasons plus part of a fourth. Moreover - and this is so painful - they never won a SB with Moss. They won all their Super Bowls with non-#1 wide receivers.
Now they did it differently for sure. Here's who, IMO, were the "#1" receivers on the team each year under BB (starting in 2001):
2001: Troy Brown - 101 rec, 1199 yds, 11.9 ypc, 5 td (Pats go 11-5, win SB)
2002: Troy Brown - 97 rec, 890 yds, 9.2 ypc, 3 td (Pats go 9-7, miss playoffs)
2003: Deion Branch - 57 rec, 803 yds, 14.1 ypc, 3 td (Pats go 14-2, win SB)
2004: David Patten - 44 rec, 800 yds, 18.2 ypc, 7 td (Pats go 14-2, win SB)
2005: Deion Branch - 78 rec, 998 yds, 12.8 ypc, 5 td (Pats go 10-6, lose in divisional round)
2006: Reche Caldwell - 61 rec, 760 yds, 12.5 ypc, 4 td (Pats go 12-4, lose in AFCCG)
2007: Randy Moss - 98 rec, 1493 yds, 15.2 ypc, 23 td (Pats go 16-0, lose in SB)*
2008: Randy Moss - 69 rec, 1008 yds, 14.6 ypc, 11 td (Pats go 11-5, miss playoffs, no Brady)*
2009: Randy Moss - 83 rec, 1264 yds, 15.2 ypc, 13 td (Pats go 10-6, lose in WC round)*
2010: Wes Welker - 86 rec, 848 yds, 9.9 ypc, 7 td (Pats go 14-2, lose in divisional round)
2011: Rob Gronkowski - 90 rec, 1327 yds, 14.7 ypc, 17 td (Pats go 13-3, lose in SB)
2012: Wes Welker - 118 rec, 1354 yds, 11.5 ypc, 6 td (Pats go 12-4, lose in AFCCG)
2013: Julian Edelman - 105 rec, 1056 yds, 10.1 ypc, 6 td (Pats go 12-4, lose in AFCCG)
2014: Rob Gronkowski - 82 rec, 1124 yds, 13.7 ypc, 12 td (Pats go 12-4, win SB)
2015: Rob Gronkowski - 72 rec, 1176 yds, 16.3 ypc, 11 td (Pats go 12-4, lose in AFCCG)
2016: Julian Edelman - 98 rec, 1106 yds, 11.3 ypc, 3 td (Pats go 14-2, win SB)
2017: Rob Gronkowski - 69 rec, 1084 yds, 15.7 ypc, 8 td (Pats go 13-3, lose in SB)
2018: Julian Edelman - 74 rec, 850 yds, 11.5 ypc, 6 td (Pats go 11-5, win SB)**
2019: Julian Edelman - 100 rec, 1117 yds, 11.2 ypc, 6 td (Pats go 12-4, lose in divisional round)
2020: Jakobi Meyers - 59 rec, 729 yds, 12.4 ypc, 0 td (Pats go 7-9 and miss playoffs, Cam as QB)
2021: Jakobi Meyers - 83 rec, 866 yds, 10.4 ypc, 2 td (Pats go 10-7, lose in WC round, Mac as QB)
*Wes Welker those years put up sick, sick numbers. But I contend that Moss was still their #1 receiver.
**James White had more catches and TD than Edelman, but it's really hard for me to put a RB as a #1 receiver.
I mean, the've won a TON of games and a TON of Super Bowls without a true #1 receiver (depending on how you define that). Clearly you don't need a true #1 WR in order to win a Super Bowl. What you need is GOOD receivers, and preferably a lot of them. So you spread out a defense with 4 WR, and if you've got 4 quality WRs who can all win against man coverage, generally teams don't have enough quality DBs to cover that many good receivers, so you're going to get a really good matchup somewhere. Right now the Pats don't have that. They've got basically 2 good WRs and 1 good TE, and it's not *that* hard to defend.