Playing more will always be the answer to improvement. It doesn't happen overnight and doesn't happen because you tweak some settings or buy some fancy peripherals or whatever. The best advice to give would be on what to play and how much playing. If you can't accept that playing more is the key to improvement, then I wish you luck in ever improving.
What to play:
To improve on HR, I recommend to try stuff that is out of your comfort zone, but not impossible for you to play either (say rains with HR or something) and add Nofail. Below rains (salads, platters) won't help much on HR as there is little to no flow when playing and (sometimes) a lot of memorisation. Rains are also where the CS starts becoming uncomfortable for a lot of nomod players (4 with HR is 5.2) though you did mention you are not bothered with CS.
How much you should play:
In my opinion, you don't need to play a crazy amount of hours a day if you want to get good at HR. It's possible, but for a lot of people this can result in mindblock (not everyone, but in general). Dedicating 1 hour on days where you have time to play (doesn't have to be every day, can be just weekends) is likely already enough to see improvement after some weeks. Also, I recommend not trying the same map too many times. When you do that, it becomes a matter of memorisation moreso than actually trying to play HR. Maybe dedicate at most 15-20 tries a map? Try not to restart too quickly either. Remember, you're playing to improve not to set scores.