[POV: You have fallen victim to numerous SEN threads just replying over and over again]
On a serious note, Sentinels criticism has been reasonable to a certain extent, but we exclude the braindead slander from here. We have seen them dominate and how they could always make it work even with comps which someone would characterize as "off-meta", as their teamwork always emerged victorious due to how good these players are.
Problem with team comps - Certainly these guys lack depth when it comes to their agent pools, as they are not capitalizing on some "must-pick agents" on certain maps. Additionally, their team comps have become predictable and are often easily counterable. For example, Shazam plays Sova very well even on maps where Sova has been pushed out of meta by other initiators, but it definitely hurts his fragging potential (which he was known for) on those maps.
Overreliance on TenZ - I hated this take originally, but it still holds little weight, so I couldn't fully ignore it. It seems like Sentinels sometimes (emphasis on the word sometimes) have a problem with helping him out on T-side. Timings on entries of his teammates are just off and they often result in him getting picked off early into a site take, putting them into a disadvantageous position when it comes to trading.
Lack of teamwork - And this one is the most obvious one, unfortunately... What made Sentinels the giants they were was just the way they would, at times even flawlessly, execute sites, play retakes and just play the trade game to their advantage. Yes, even back then people joked "TenZ go kill", the thing is, he was never not set up properly by his team to "go kill" like seen recently. Lately, everything looked sloppy or was just timed awfully.
Sick on smokes - Look, I see why they wanted to include Kanpeki into the team, but personally, I would never move probably Top 5 flex player into a controller role. His performance was lackluster and his decision-making while on Omen has been questionable. I wish to see him back in the aggressive initiator & secondary entry role, where he excels at.
To conclude - As fans of the game, we cannot know why, when, and what went wrong for Sentinels. Obviously, we see the in-game performance and the obvious issues, as stated above, but we cannot know the root of that problem. At times, it even seems that the relationships have been damaged and the internal issues needed to be addressed sometimes (mainly the whole Zombs thing), but I seriously doubt it is the only issue. I also highly doubt that their streaming is getting in the way of their scrims and practices, as if these things presented issues, they would have been addressed by managers.
Unfortunately, at this point, in my eyes, it is better to hit the reset button and decide what your core is or who you want to keep on the team to start from scratch. I do genuinely believe that this is the best-case scenario for both organization and the players. Shaz, TenZ, Sick & dapr are all individuals who have proven themselves as top dogs in Valorant, but environment change and a mental reset could prove to be more beneficial to them than forcefully trying to fix every single thing that is not clicking for them. In my opinion, Shazam is the first one that would need to be benched and any other roster moves would be decided after it. This statement has zero correlation with people's perception and criticism people have of him (slander I find uncalled for at times). It comes from a perspective of knowing how crucial IGL is for the internal culture of the organization, team structure, and leadership. If roster reset is bound to happen, with these things in mind, Shazam would need to be the first one to be benched and given the opportunity to explore free agency. Any further roster change would be dumb to even predict as we are never gonna be in a position to know which players are gonna be available and how roles would be shifted according to the potential changes.