1. And if he has a somewhat decent team that has his back while you on the other hand are getting DTed by lonestar and another naut? (quite survivalable if you get lucky). Plus unless your using a mic theirs not much you can do to get your team to triple/double team him.
2. If he's spamming dynamite clunk and derpl can get around it, but what about all the other 6 characters? (with the exception of voltars hovering and yuri's flying
3. The hitbox of the bull in narrow lanes are extremely hard to dodge unless you kill it quickly which would probably require using a skill. Then your 1 well needed skill less that you could be using to kill lonestar.
Now i dont claim to be the best at this game, but there are ways around the scenarios you describe, you just have to know the situation you are in and which tools to use to get around them.
1. the issue you describe has less to do with lonestar and more to do with how this game works in general. if one player has a decent team and you do not, then youre most likely not going to win. doesnt matter if they pick lonestar or not. make some friends, play with them regularly, and teach people how to play better if need be, then this wont be so much of an issue.
2. so as it has already been stated, derpl and clunk can get around the dynamite mines by staggering their jumps to stay in the air. voltar can hover and yuri can fly to avoid them. lonestar can use bull or double/tri-jump across, froggy can splash across. for leon, its a bit tougher, but he can use moving clones to help clear the field. not real sure what cocos answer for it is though. now of course you have to pay attention to where youre walking in the heat of battle and it may not be super easy, but everyone has a way to make lonstar's mines not as effective as you may think except coco. although, if everyone had a way to make an ability not that good, then there would be no use in putting it in your load out.
3. so yes, in narrow lanes, the bull can be hard to avoid. like you said, though, you can use an ability to get through it quickly. so you have that option if you so choose. lonestar had to use an ability to fire the bull out, so it only makes sense that you would have to use one of yours to get rid of it because if everyone had a way to get rid/around it without using an ability, then, again, the bull would be useless. personally, what i do when i see lonestar fire a bull out is retreat. reason one is that its gonna be pushing me back anyway so im just gonna get out of range just in case he has the exploding bull. reason two is that if i keep holding forward, it will keep bouncing me and make me an easier target for lonestar to shoot/throw dynamite at. try that and see if that helps you out.
TLDR: im not saying lonestars abilities arent good. they are, and i would welcome a slight damage nerf to trinamite and hes the second character i play the most behind only froggy. however, there are ways and abilities you can use to lessen the amount of effectiveness that they have, you just have to be resourceful and aware of the situation.