Without a doubt, he hasn't been horrible, however over the past 2 seasons these are his noticeable signings.
Loop
2018/2019
Jefferson Lerma - 25 milion
Dominic Solanke - 20 million
Diego Rico - 13 million
Chris Mephem - 12 million
David Brooks - 10 million
2019/2020
Arnaut Danjuma - 16 million
Philip Billing - 15 million
Lloyd Kelly - 13 million
Jack Stacey - 4 million
Very few of these have proven to be anywhere near Premier League quality, David Brooks has been brilliant, and Billing hasn't been too bad and would probably do ok in other bottom half sides, but other than those two I struggle to see any value for money in any of these signings, although Jack Stacey was only 4 million, and came in to be a rotation option.
Add to this that some of the departures have been a little naive if you ask me. Yes they got a good bit of money for Mings, but he's been one of the reasons Aston Villa have stayed up this season, and Mousset has had a decent enough season with Sheffield United.
They can't all be instant winners, name me a manager thats only signed successful players?
The key is getting the majority right which is what he did throughout his time there. Also the players mentioned, its too early to right off the likes of Kelly, Mephem and even Solanke.
Take Solanke for example, dropping down to Championship is a good thing imo, he's definitely got talent but too much has been expected from him too soon. Deemed a English wonderkid at Chelsea, than Liverpool and then a big money transfer, that's a lot for someone that's done nothing at the top level. Learning his trade in the Championship and getting used to consistently scoring goals in the men's game would be very beneficial for his confidence.
Ibe definitely was cock up, and the only true write off, he has a terrible attitude, offered nothing and they got nothing for him, he can't even get club to sign him on a free....
With regards to Mings & Mousset they made money on them so am not sure how they are deemed as failures on Bournemouth's part.
Tbh, I can't think of many teams that have gone down that had such a pool of talent which lots of clubs are going to want, Leeds are probably the other, which looking back was pretty amazing, Smith, Viduka, Kewell, Milner, Lennon to name a few...
Bournemouth can get rid of Ake (40m, Wilson(35m), Brooks(40m) & King(20m) and make back around 135m (would be near 160m had they cashed in on Fraser) thats alot for a relegated team and would put them in a positive territory for their net spend (-133m now) over the 5 years they were in the PL.
Imo, had just one of Brooks, Wilson or Fraser been fit and committed for the whole season they would have definitely stayed up.