First, the most basic and important thing
THERE IS NO MAP CONTROL
The 1on1 games are not just about running around and fragging, they are all about map control. For example in Quake 3/4/L you need to time Armours every 25 seconds and Megahealth every 35 seconds, additionaly you can control weapons by zoning enemy out of them. In Unreal Tournament you time Armours every 27.5 seconds, Shield Belt every 55 seconds, and weapons every 27.5 as well. Players fight for those advantages, it is main force behind them moving around the map and their tactics.
Well, there is one bit of map control, health pickups. However in other 1on1 games the health pickups can only be taken if your health isnt full. While this was originally because single player worked that way, it was kept in later multiplayer only games to stop players who are in control from starving their enemy. This meant that if player who was in control, stacked with health and armour, wanted to deny enemy from regaining health, the only resource player out of control have, would have to shoot himself which would reduce his armour as well. Basically a tactical trade off that some players may want to take at certain times.
In Project 1vs1 health pickups may be taken at any time, every 30 seconds, so the only possible tactic is to control them after dealing damage to the enemy. That is whole map control and tactical possibility that Project 1vs1 has.
Now, for the rest of the feedback
KIND OF HERO SHOOTER
For competitive fpp player the defining feature of hero shooters are not heroes, but the limitations they come with. That is limitations of available weapons and abilities, as well as starting with them all. From that point of view, the only difference in Project 1vs1 is that instead of just taking loadouts predefined by game designers, we are able to create loadouts ourselves. This is not a complain, but a small warning. Not a one hero shooter managed to become played in 1on1, neither did any fpp shooter with such limitations.
KIND OF LOW BUDGED FEEL
I know that this is the very beginning of creating the game, but everything about it feels very plastic. You should be knowledgeable about importance of weapon feedback that is created by animation and sound. The problem is the whole game feels like that, weight of moving around, jumping, everything seem disconnected from the player. A lot of low budged fpp games are like that. This is very hard to define, but I think you probably know that and are working on it.
You are aiming for as wide audience as possible, but you are also coming to kind of oldschool and hardcore territory. A territory full of dinosaurs who need their specific settings and hardware. Even if you work hard on that, there still will be a lot of complains from people who cant get something to work as they like. So let me start with mine. The launcher where you manage your whole game is too big and cannot be scrolled or scaled down. It doesnt fit the 1024 width, and while you can just move the window around, you cant move it when there is a message window like when you get the loot. When I got the loot window, the only thing I was able to do was to click on 2 pixel sized edge of unknown yellow button on far right side that didnt fit the screen.
There will be more people who are using lower resolutions in Project 1vs1 than in the games you worked on before. There will be more people using 4:3 screens, there will be more people with CRT screens that dont display LCD fonts well, there will be more people using some outdated or unusual settings and hardware. You are entering a real PC territory where players are spending many hours just to work on their config files.
This is probably something that you already have heard from other players, but 1on1 games tend to have movement methods. Currently you have those in form of abilities like Air Jump and Railgun walking, but for now that is very little and when you create more you should try things that feel analogue, not just hit the button to activate a move. You can probably make a good game even without any advanced movement, but you really need to make your design idea work.
Well, for now the game is just boring. It is just very simplistic.
Two examples of failed games you should look at as a warning
LawBreakers - tried to find a niche that didnt exist, hero shooter limitations and too much hitscan alienated oldschool arena shooters players, while the game wasnt good enough hero shooter to get players from those
Shootmania Storm - a game that tried to limit itself and base around simplicity of insta gib mode that was always played a lot as a side dish in arena shooters, however it was just too simple and became boring right away