My random idiot's take on current tactics:
While complaints about individual player errors in the last few matches all have merit, these are secondary to the main problem which has been the tactics. I don't like the 4-3-3. It gives us an attack-defence balance which tilts us one player too many towards attack. In our winning run last season, we played a lop-sided 4-2-3-1 where the left attacking midfielder (Sibbald or Holt) played deeper and narrower, while the right attacking midfielder (Mullin) pushed up high and wide. This effectively meant two outright attackers. The 4-3-3 we've been playing this season has given us three outright attackers; Anderson, Forrest and a right winger (Bailey for last two matches). We're not good enough to play with this extra attacker compared to last season's set up. So drop the right winger and return to the lop-sided 4-2-3-1 with Forrest as a high, attacking left midfielder and the right midfielder - Shinnie or Sibbald - deeper and narrower.
We're expansive in possession with the 4-3-3 and again this doesn't play to our strengths as it shifts our attacking focus down the flanks rather than more central play. In the last three seasons, short passing moves in central areas always involving Pittman or sometimes longer passes to a central target to chase has been our common goal route. Flank play and crossing has featured, of course, but not commonly. The 4-3-3 sees our wingers pin to wide starting positions and spreads out our central midfielders. The wider and deeper starting positions for the central midfielders makes it hard for them to get in the box and attack the crosses which later arrive. The 4-3-3 sees the "number 10" space left vacant, a particular crime for us given Pittman's excellent ability to operate there.
Compared to the 4-2-3-1, the 4-3-3 not only causes greater spacing between players when in possession but also when in defensive formation. In the 4-3-3, our midfield trio have been having to run like mad men to plug all the gaps left by the wingers remaining higher. The compact 4-2-3-1 was much more solid defensively as only one wide player was remaining high rather than two. The 4-2-3-1 also gave the option to play an outright destroyer as one of the holding midfield duo (Bartley for the last two seasons) and two holders provide more insurance for the attacking runs of Longridge and especially Devlin.
As for the switching to 5-3-2/5-3-1-1 after an hour, this in itself isn't a problem if it suits the match. It can simultaneously give more defensive cover as well as more forward presence. That can be a smart move if the game has become "end to end" with the midfield being bypassed and patient build up being replaced by direct counter attacking. The problem here is player selection not tactics. We commonly switched to a back 5 to see out matches in both the previous two seasons but often Ciaron Brown was the central defender being brought on. Brown was a presser, a stopper-type who attacks the ball. Kelly is the opposite, he exclusively defends by covering, by dropping off. Brown's aggressive positioning meant our back line remained high whereas Kelly's introduction in the last three games have dropped our defensive line back, inviting the opposition onto us.
Conlcuding sentence; the 4-3-3 doesn't suit us and a return to the lop-sided 4-2-3-1 of the previous two seasons is needed.