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The brain can only learn one thing at a time, so if you are concentrating on your fretting hand you will struggle with rhythm and visa versa.
The key to learning anything on the guitar is isolation. Just practice rhythm with the fretting hand just holding a chord or better yet muting the strings. Then switch to learning the fretting hand stuff and just strum once per measure. Over time you will get better at both and it will be easier to combine them.
The other key is to slow things down. When using a metronome you should be constantly adjusting the speed. If you play something 3 times in a row an make mistakes then slow it down, if you can play something 3 times in a row with no mistakes then speed it up. Typically you can make adjustments in 5 to 10 bpm increments, although I’ve had complicated rhythms where I had to increase by 1 bpm per day for several weeks to get the timing right.
I also highly recommend the book The Laws of Brainjo, it is great at explaining how the brain learns especially related to guitar/banjo.