Lampard was just a temporary manager for Chelsea and he wasn't expected to do bigger things much. Because Chelsea tried Lampard as a permanent manager before as well but it didn't work out well at all as you remember. Lampard just doesn't have it in himself. He couldn't do well at Everton either so I think it would be better for his career to do a different job then being a manager.
Pochettino is a decent manager and I feel myself confident about him to do much better than Lampard. If Chelsea build their lineup in a solid way I think they will be competitive for top 4 again in a short time.
This season I see Lampard only being the scapegoat for Chelsea's failures this season, how could he not, he was appointed to handle Chelsea when everything was destroyed. And it becomes a gamble too if he is expected to make a difference in the game at that time. Instead of a good change that can be shown, in fact what happened is the opposite. I won't say anything about Chelsea's failure under Lampard's coaching, because basically the team is in a very bad state after the 2 previous coaches.
I see it totally normal that Mudryk didn't perform very impressively this season. Because the whole squad of Chelsea were very inadequate. Their morale was so low that they even gave up on the season quite early. In this situation it wouldn't be a healthy assessment about a player. There is a new period starting for Chelsea now with Pochettino. This is going to be the most important time period to watch Mudryk's capabilities. If the team make a good start the expectation from him will also be high.
If he still can't impress people then I will also agree with the people who think he isn't good enough for Chelsea.
I would even say that all the top players who are at Chelsea this season are normal if they don't play to their fullest because the club's condition is not very promising overall. This has had an effect on other players who have received a lot of criticism because they are considered unable to help the club to slowly develop and improve their overall performance. Maybe our views will differ when we see the team playing well but the players don't show anything good, and that's normal when they get a lot of criticism because of their individual play.