That's a skill issue, but I admit it's harder to upgrade weapons. It is easier than ever, especially on android to get more gems. Just yesterday I got 1.5k gems by reaching level 20 on another app on the gem offers.
You can quickly get the lottery weapons through farming for several days.
You can also get a weapon that is part of a set event with only 780 gems at max or less, previously you needed 3k gems for one event set weapon.
Also now there is a Trader's van and they can sell weapons for 500 gems or more.
Also now you can get 80 lottery keys per day, 1000 clan silver per day, 45 coins per day, 30 gems per day, and 20 battle pass tickets per day JUST BY WATCHING ADS
With all that and enough persistence I managed to get 2 battle passes for free,
I REFUSE TO BUY THE NEW SATANIC BATTLE PASS BECAUSE I AM A GOOD CHRISTIAN AND GOD WILL SEND ME TO HELL FOR BUYING WEAPONS ON A VIDEO GAME :v And each battle pass gives you 4 new cool weapons.
While Pixel Gun 3D is a pay-to-win game, you can still get all weapons for free with enough patience and effort.
See this? I have the strongest weapon in the game, The Ultimatum, and I obtained it just by farming WITHOUT PAYING A SINGLE CENT. Free-to-play players can still keep up with p2w players, especially nowadays since now, you can still get the strongest weapons for free with enough time and effort, paying for the game is just a small boost, not an advantage.