No, we're not expecting Neymar and Mbappe, we're expecting players to come in to fill in the holes of the squad. That didn't happen last summer, and arguably it didn't the summer before either.
Cast your mind back to the end of last season, and everyone said our major targets should be at least three of the following: CM, RW, LB, DM, CB - all of whom should be first team quality to relegate the current players we have in those positions to squad player status. What ended up happening was we got an AM for seemingly little reason, two teenage RWs who are long-term projects, and a LB who has maybe done his part in forcing the LB we had to up his game, as well as a striker who we could have gotten at any point since last March but decided to get him on deadline day so he missed the first month of the season unnecessarily. Arguably not one of those signings filled any of those needs and instead just bloated a squad which Ole had previously done well to trim the excess fat from.
Then, when we go back to the summer previous to that, we had to let go of Sanchez, Lukaku, Herrera, Fellaini, Valencia, Smalling - all players who had an important role to play under the previous manager and who needed replacing, in addition to the longstanding need for a RW and AM. What ended up happening instead was we got replacements for Valencia and Smalling but Ole had to risk his job and the whole season on Pereira and Lingard stepping up to fill the creative void and Martial + a 17 year old Greenwood to replace Lukaku. If it wasn't for Bruno, then he would have been out of the job and through no fault of his own because he did his part in selling the players that needed selling and the board didn't do theirs in getting him the adequate replacements for some of those who left. Primarily Sanchez and Lukaku.
The windows have only been fine in hindsight, because unlike Jose, Ole isn't a cnut and has made do with the scraps he's been given rather than agitate for more. By their second transfer windows, Jose and LvG had spent c.£750m between them in their tenures. Ole is likely going to be barely reaching half of that figure after three summer windows, with a bootload more outgoings which have paid for most of his outlay. The depth of support Ole has had doesn't match the support that Jose and LvG got.