Honestly Erik ten Hag has gotten enough time to turn things around for good at Man Utd, he had so far signed 16 players loan and permanent players yet the club hasn't achieve their great status due to their inconsistency in the team performance, majority of his new signings had flopped, the likes of Onana, Antony, Mason Mount, Lisandro Martínez and Tyrell Malacia hadn't perform as expected despite huge sign on paid to secure their services except Casimero, Eriksen and Rasmus Højlund who had proven their worth but injury problems had reduced their impact in the team, Rashford, Martial had lost form, while Sancho who ought have help the team is not in the good book of Erik ten Hag, I think the manager had all the time at his disposal to up the team game or performance yet not yielding any positive results.
Among the names you mentioned, I think Martinez, Casemiro, and Eriksen are decent signings under Ten Hag, but all of them only performed well in one season. Martinez played well, but unfortunately, he suffered an injury too early. Casemiro, who was a mainstay for MU last season, is playing below his usual form this season, likely due to excessive workload and frequent injuries. Eriksen, on the other hand, hasn't been favored by Ten Hag.
As for the remaining names, they are truly disappointing. Do you think Hojlund has proven his worth? Remember that MU had to spend £72 million to acquire him, and what has he contributed? He hasn't scored a single goal in the Premier League, which is a dismal record. Regarding Mount, Ten Hag brought him back from Chelsea but seems unsure how to utilize him, leading to frequent bench appearances and a decline in form.
In a fair assessment, Ten Hag has a squad with many good players that other teams envy, but so far, he's struggling with his football philosophy and somewhat stern personality, creating an unstable team. Their poor performance is evident.