You can always play a maj. triad to replace a dom. 7th chord (without a b5 or #5) if you don't like the sound of the seventh.

What is the point of the seventh? It increases the sense of tension. Why? Because people think it does. How does it work? It "resolves" to the third or the fifth of the tonic. So now we're talking about "voice leading" which, in a sense, is what this is all in aid of. For example:

G --> G (it stays where it is)
B --> C
D --> C or --> E (take your pick)
F --> E or --> G (take your pick)

In many kinds of music, composers and players strive for "smooth voice leading", which most will agree is a nice sound, but not the only nice sound.

A guitar provides many ways of getting from one chord to another and there are many different sounds that one can get from a single chord change. A good place to start is a cadence, i.e., subdominant, dominant, tonic, e.g., F G C or Dm7 G7 C (the Dm7 has a subdominant function here --- if you like the functional approach to harmony). Plenty to experiment with here, if anyone wants to play this sequence in various ways paying attention to the voice leading. I recommend switching keys to prevent boredom and definitely use alterations!

What really helped me to learn my chords, scales and arpeggios was playing "chord melodies", i.e, playing a melody and finding voicings for the harmony with the melody on top. The chords will tend to fall into a pattern, as mentioned above.