Marchessault and Stamkos can create their own looks and aren't reliant on their line-mates to dictate their success. Marchessault is a dynamic goal scorer, scores goals multiple different ways. And he can carry the puck and make plays. Neither are the ideal solution although Marchessault fits the bill more than Stamkos who is less dynamic.
At the end of the day, there are only two types of forwards, those who drive and create, and those who read and compliment their line-mates. The Bruins are loaded with complimentary guys (Zacha, Geekie, Coyle, Frederic, Debrusk and Heinen if either return). Complimentary isn't a knock, it just means more consideration needs to be taken into where they play, who they play with, and how they fit into the overall composition.
Lindholm is a fine player. He can help any line. The issue is if you want to get the most out of him relative to what you are playing him he needs the right line-mates and they just don't have that right now and that should be the priority. He comes in at 8 million per, you need him up around 25-30 goals, 75-80 pts. and I don't think he can do that here unless better players are also added. I'm not giving a guy 8 million to be a 50-55 point two-way center. He'll never come close to that 2021-22 season regardless. I'd bet my house on it.
This is like going car shopping. Your partner really wants a new Corvette to keep them happy, but there are no Corvettes on the market so you come home with a Honda Accord (Lindholm). Solid, reliable car. But now your money tied up and when that Corvette you really need hits the market you have no way to pay for it.
Bruins need to leave the Accords on the lot and focus on a new Corvette even if they have to wait.