There are still only 4 WRs on the roster, right? I know Miles was used as a receiver early in his career, but they simply need more receivers.
Keep in mind they can activate 2 PS players each week, so it could be they already know who they want to activate week 1.
Also it is Detroit. We may only need to throw 5 passes before we have an insurmountable lead 
This is kind of undermining the point. Yes, the team could call up a WR to return kicks and be a below league average WR, but why is a 4th RB, who doesn't return kicks, added in that spot?
True, I assume they see Sermon as a project / possible talent that could provide more. Maybe he can return kickoffs, not sure, that is much easier than punts, which is a more difficult learned skill.
If it means the team could gain picks for Gainwell or Scott, then I think it's a great lateral move.
They had to put Sermon on the 53 because they claimed him on waivers. They may demote him to the PS later, and replace him with a wideout.
Dillard's injury puts a lot of pressure on Mailata to stay healthy. Awosika and Sills do not inspire confidence at LT.
It still leaves a giant hole at WR and kick coverage depth. I am fine with maximizing value and moving pieces around, but I feel like the eagles needs are face-up at this point.
They have Allen, Cain, and Covey available at receiver on the PS, and 4 great players on the 53 at that position. There is no giant hole. There is not even a small hole. In fact, they have one of the best WR groups in the entire league. If they lose, it's not going to be because they chose the wrong #5 WR to activate. I seriously don't get what you are trying to say.
I'm trying to say they are incredibly thin at WR outside of the 4 on the roster. Let's not pretend that some PS players are a sign of strength.
EDIT: do you think having only 4 WRs and 4 RBs is a good idea in the modern NFL?
They are carrying 7 WRs. Under the current practice squad rules, where you can elevate two guys every game, PS players ARE your depth. Cain is better than the 5th wide receiver on any NFC East team, better than Reagor (who is #4 on the Vikings), better than the Chief's rookie, etc. And they have two other guys who have shown potential that they are developing. I'm fine with their wide receiver room. Who did you want them to carry? Reagor?
And I can't find a single team that is carrying more than 4 RBs on their 53 on the ESPN depth charts.
You have an odd fascination with what other teams are doing. The better argument is if RBs or special teams matter in the current/future NFL.
If having more than four RBs were important in the current NFL, then the teams in the current NFL would have them.
They could have kept Hightower, but didn't view him as a legit #5, I guess. Ward was hurt. They'll coach the guys on the practice squad. They should be able to fill in as 5s, if needed later in season. You have to protect the quality players under your control. Reagor wasn't worth keeping. I'm fine with what they did. They have better WRs this season than last. Reagor played a lot last year and was awful. Arcega-Whiteside was a blocker, who couldn't avoid penalties. The Eagles have moved away from their past draft blunders. That's a good thing. We are actually carrying 4 real WRs this season. That wasn't the case last season.
Taylor went unclaimed and is on the practice squad. Unless there are any more moves coming (I wouldn't put it past Howie), with the Dillard news and the lack of the returner, it's a safe bet the practice squad call ups for week one will be Covey and Clark.
I know. Perfectly fine, IMHO. The natural question back to you is: fine to complain, but be specific. Which two players would you like to see removed from the 53-man roster and which 2 would you want to see added. You can't say Dillard, he wasn't a choice, other than to cut.
How so? He is a RB on the roster. If they want to swap him with a RB now on the practice squad, they will be able to do that. Sermon seems a guy worth a shot. You didn't answer either question. Whom would you add to 53-man and whom would you drop? Sermon is young and cheap. Better than Howard on the roster.