But the beauty of time travel is that you don't say goodbye to everyone in your life, you just pop off to have a few adventures and return a second or so after you left - a concept that was briefly covered in "The Power of Three" (series 7).
As for The Cybermen and Daleks, I believe there's a bit BBC emotional baggage involved, as there is with me having watched the Daleks since their inception in 1963. However, I agree that the "Dark Water/Death in Heaven" stories were a bit wishy-washy, though I cannot agree about the lack of originality/being better.
Here are a few worthy of mention...
S1 The Empty Child/The Doctor Dances
S2 Tooth and Claw School Reunion (The return of the late Elisabeth Sladen as Sarah Jane Smith) The Girl in the Fireplace
S3 The Shakespeare Code Human Nature/The Family of Blood Blink
S4 The Unicorn and the Wasp Silence in the Library/Forest of the Dead
S5 Time of the Angels/Flesh and Stone Vincent and the Doctor The Lodger The Pandorica Opens/The Big Bang
S6 The Impossible Astronaut/Day of the Moon The Doctor's Wife A Good Man Goes to War/Let's Kill Hitler