There area a few fundamental flaws in your argument...
1) If Tolbert gets 100 passes his way that would be excellent and put him into legitimate WR2 territory. Last season Jameson Williams got 92 targets (1.97Y/RR) playing sharing targets with St. Brown and LaPorta. Cooper Kupp got 105 targets (1.88Y/RR) despite being #2 to Nacua and missing several games. Tee Higgins got 104 targets (2.05 Y/RR) despite missing multiple games and playing with Jamarr Chase. You can keep going down the list too and see plenty of teams with high volume WR1s getting other guys around 100 targets or more (Indy, Minn, Sea, etc.).
Based on his snap count from a year ago 100 targets is about what should have been expected from Tolbert. His production is about 25% less than you’d like to see. And from your example if Tolbert catches 70% of his targets for 2.8Y/RR hes going to be in the hall of fame one day. Thats the top 1% of WRs doing that.
2) 200 targets for a WR is typically an outlier number. Only 3 guys in league history have broken the 200 target mark with 205 being the single season record (Marvin Harrison). Lamb did come pretty close a couple years ago, but 150 is a much more likely number out of your WR1 on average. Also 500 attempts from your QB in this era is pretty low. Over half the QBs in the league threw over 500 attempts and many others simply didnt hit it because of missed time. Dak himself in 2024 was on pace for 607 pass attempts, and had 650 attempts in 2024 when Lamb had so many targets. Basically there are plenty of passing targets to go around to multiple players in the NFL.
3) You're pretty much suggesting that teams are force feeding certain guys and the WR has no responsibilities pre throw to get the QB to deliver them the football. There are certainly a hand full of plays each game designed to get a certain player the football, but the majority of pass plays are just designed to get the open man the football. The reason Tolbert isnt getting the football more often is because he is not getting open at a high rate. All QBs are going to be guilty of missing an open WR on occasion, but over the course of 17 games that should even out to where most WRs will be on a pretty level playing field of missed opportunities.
This has always been part of the issue with Tolbert. Depending on the coverage he can be useful in some crossing & inside cutting routes, but he's dominantly a vertical part of the route tree guy which will limit how often the football goes his was. If he wants more targets he needs to continue his development as a complete WR. That has way more to do with his target share than it does Lamb.