I found there was a disconnect with the tone, theme and setting for the final push.
I never felt like this was an all or nothing gamble, that the reapers where this all powerful galaxy destroying force. Why? because I killed Sovereign, killed a destroyer with the Quarian fleet while it targeted me on the ground and watched a thresher maw kill a different destroyer. Couple this to the fact that EVERY time I ran into a problem I could pull the super dooper awesome trooper Shepard move and take out the staples "easy" button and press that for a cost free victory.
By the time I reached priority Earth I never felt like I was fighting this desperate battle to survive but I felt like I was fighting in battle that the reapers were doomed to die in. That's a TERRIBLE disconnect to have for the theme of the series. Sometimes in games you want to feel empowered, but not all games should make you feel empowered, its a death nail for a horror/survival genre game to feel kickass and empowered. Playing Shepard should not have felt so god damn super dooper awesome after fighting to unite the galaxy. They should have made the game feel like it was a desperate gamble that you were not likely to "win" it is why the dream sequences all feel like forced emotionally because why is Shepard depressed and fearful? The gameplay, mechanics and story all show Shepard kicking ass and taking names, all show Shepard pushing away entrenched problems of the galactic community away with a mere way of the hand. Nothing is costly, no hard choices, no loss in Shepard's personal orbit directly tied to the reapers.
Hell Shepard is superfluous to the overall plan on earth as you are not even assigned to a critical unit or sector, its just "run around as you see fit Shep we got this." That doesn't add to the tone of a desperate last chance for victory battle but more of "Reapers? Meh they are tough but we got this, no worries." attitude.
All the work you put into the series in amassing this war score means nothing to the overall content of earth. There seems to be no tangible, or emotional connection to choices you made in the series, during the operation on earth. You then get a mad rush at the end that even with the extended cuts leaves you with a cognitive dissonance because the desperation of the fight just never translated well. Its also explains why so many people wanted the option to say "go to hell" to the catalyst which they added in EC but as an auto reaper win. This fan base response happens because the game made you feel like you could defeat the reapers on your own terms not that you are just barely struggling to survive that this is the end unless there is a miracle.
You may not feel that this is detailed enough but the failures of ME3 where not so much this level design was too X or the mobs were too Y. The failures where in how the mechanics worked at cross purposes with creating the feel that you are desperate that there isn't much hope, that the reapers are so overpowering, that your ability as the player/Shepard to defeat them is in question. To do this they needed to make you feel progressively less empowered as the story unfolded in ME3 but you felt more and more empowered with each crisis solved with a magic wave of the hand using the "I win" button. This is why I think the endings fail so badly, if the game made you actually feel like you would most likely lose, there would be disappointment that the previous choices has less impact than player would have hopped but that is the norm for games so I believe the rage would have been muted, but you felt so god damn super dooper awesome when you get to earth that when you are presented with the choices you don't feel like this is the "hail Mary" the crucible is meant to feel like, so the conversation with the Ai just seems forced and jarring which shatters any hope of a satisfied feeling for the game/series.