Regarding receivers, it obviously is better if you have better receivers but as someone else said I think the O-Line is more important than the receivers in terms of having the tools to allow a QB to be successful or for a team to have a good passing game. And I am more concerned with the O-Line than I am the receivers. The OL may be fine, Belichick has a way of figuring that out, but there are questions. We will likely start at least 1 rookie and others that are not fully proven.
I think Mac Jones is plenty good enough to get the ball to these receivers if he has the time. And I think these receivers, when you consider them in total including backs and TEs, are good enough to get open. Maybe not big explosive plays all that often, but enough to keep the ball moving.
Joe Flacco was a super bowl QB for example and he didn't have super star receivers. Anquan Boldin I guess was pretty good, maybe better than any of our receivers, but Ray Rice led the team in receptions that year. And the O-Line was very good and they had a running game that had to be respected. All that allowed Flacco to be a super bowl MVP.