Not sure what year/model or the faucet you have, but here are some generic comments which might help.
This is going to be "assuming" your hot and cold water in the shower are both having low pressure, if this is only the hot or only the cold, then we need more info to help better. This also assumes the kitchen, bath and toilet have adequate water pressure, if not then we need more info also as both of these can point to a plumbing or pump issue.
The standard RV shower faucet and or shower head/wand setup is made to conserve water. This is often done by having a small disk or washer with a very small hole in it to created a fixed office to restrict the amount of water coming out the shower head. Reasoning is, the shower can use a lot of water and the onboard fresh water tank only has so much water in it, so to conserve the supply, they limit the shower and the sinks with the flow restrictors.
If you are on city water hookup, then removing the restrictor will increase the water flow. Just realize the grey water tank will fill faster too. If you are on full hookup with a sewer connection at the site, dump the tank often or let the grey water valve stay open.
Also realize, the water heater only has a 6 gallon tank supply, increasing the shower flow will use more hot water faster and you might run out of hot water too soon.
To help the entire situation and not waste water, but to get better flow, or what feels like better flow, is to do one or both of the following.
1. Upgrade the shower head to an Oxygenics RV style shower head. These limit the water but yet create a much better spray pattern to wash with. We have used one since they came out years ago, back then they only had one model, now they have many RV models.
This is the one we have, it is a slightly upgraded model, but the same basic one. https://oxygenics.com/products/bodyspa-rv/
2. If your shower head does not have a on/off knob or button, then install an on/off valve in the hose. Let the faucet stay on your hot/cold mixture but shut the sprayer off. Then do a so called "navy" shower. Wet yourself, turn off the shower head, soap up, turn shower head back on, rinse off etc. Thus getting acceptable flow when needed, but shutting the water off rather then run all the time.
We do both # 1 and 2 above as we camp most all the time with water in the fresh tank. Both of us can shower back to back and not run out of hot water and have an acceptable water spray. I will add, when we bought our Oxygenic shower head, we liked the head but did not like the stiff hose that came with it. We kept the Sunline provided hose, but used it on the Oxygenic shower head. I see now Oxygenics changed the hose, it may not be as stiff as it was years ago.
Hope this helps