Realistically, it will be hybrid model. Working from home is better for employees, not for employers. Especially large companies who have massive commitments in office space and campuses have significant financial exposure. Empty office spaces are destroying entire cities - case in point downtown San Francisco. 
Overall productivity is in question as well. In high cost areas like NY and SF/LA, companies are paying higher wages but employees are choosing to live in lower cost areas because of remote working privileges. So one may seem compensation adjustment as well. 

cannot imagine returning to office, quite a bit of productivity lost finding meeting rooms all day if meetings is what you do anyways.

I think it's unreasonable. I'm assuming they have employees all over the place, or employees that might have moved since going remote. If someone has proven their efficiency and ability to work remotely, then they should be given permission to continue to work remotely. This has become the new normal lifestyle for so many people that asking them to return to work could have severe repercussions, such as an increase in mental health issues (stress, depression, anxiety, etc.).

I think it is understandable that some companies like Amazon are asking engineers to work from the office most of the week. This allows for better collaboration, team building, and overall productivity. However, it is important to recognize that the ability to work remotely is a major benefit for many workers, and it should not be taken away without providing alternative solutions. Additionally, companies should make sure they are providing the necessary resources to make the transition to a hybrid model easier, such as providing the necessary equipment and training to work from home.

I think it's understandable for big tech companies to ask engineers to work from the office most of the week. Working in an office environment can help to foster collaboration, creativity, and communication between team members which can help to improve productivity and efficiency. Additionally, having engineers in the office can make it easier for managers to provide guidance and feedback. However, it's important to also recognize the benefits of remote work, such as improved work-life balance, cost savings, and access to a wider talent pool. Companies should strive to create a flexible work environment that allows for both in-office and remote work, depending on the needs of the project.