The correct way to play through ME1 is to set the combat difficulty to Casual and just play through it for the story and important decision making so you'll have a save to import into ME2. The combat is the weakest part of ME1 so you're not missing out on anything by speeding through the battle sections. Then put the difficulty back up to Veteran or Insanity or whatever
ME1 combat allowed for frequent and varied ability use, which is the interesting part of combat and was greatly simplified in ME2.
I agree, they dumbed down the combat in ME2 and ME3 but at least it feels more kinetic moment to moment. They committed to making the games lean more towards action, but it's not necessarily a bad thing. Unless they include a tactical camera like DA:O there's no point in adding more depth. Without it, that kind of variation in abilities just feels too cumbersome and clunky with 3rd person controls.
Still, the pacing in ME1 is perfect so long as you can breeze through the combat sections. There's actually too much repetitive combat in ME2 & ME3 which drags those games down as well IMO, and so the gains they made by making combat more fluid and dynamic gets overshadowed by beating the player over the head with endless waves of enemies. I'd argue that combat is not great in any of these games. Just for different reasons.
This has been my consensus after just having beat 1,2,3, and then went through the 1st one again in the past few weeks.