Well my posts somehow end up being overly long, so here is short answer: NO.
If you are not too lazy read further;)
One thing to note, I'm abstract thinker and like to talk about general state of affairs, quote some of my ideas here come from "though games" (think though experiment in physics), concrete examples are there, well to be examples as my experience is that other people are less likely to be abstract thinkers. This note is here to maybe help you better see from where I'm coming from.
Everything what you say about capture is mostly irrelevant, because of very simple reason: you take tiny risk once and get basically unlimited payoff forever. Since trade routes never disappear. But there is more. Yeah you can replace routes with better ones, but if it is your enemies routes, you will not do that! What is more, suppose you are allied with distant player, you build trade routes with him. Now time passes, situation changes and you need to make war with that player, and need to ally with closer neighbors. But you can't do shit about trade routes, as your ex ally is further and thus routes are more lucrative, you can not help your current ally who is closer, and you are helping your now enemy! (mind you in some upcoming version there might be some limitation on civ statuses/state transitions).
Now, as for the presistance of routes -- I made my point in GT8. You can either build bunches of costly improvements to keep your population in line, or you can build trade routes. Trade routes often speed up the game. Without them in GT8, we'd still be flinging musketballs at each other. Some may like this, some may not. They probably would have been fine in GT9, if it were not for the default science rate.
And the net result -- trade routes allow bigger armies and more action. Which is what you wanted, is it not?
Building can and do get destroyed you can attack them, they have upkeep, they normally depend on land, which again can be denied access in many ways. You can do nothing against trade routes (again replacing enemies trade routes with better is complete nonsense, and if talking about taking the city, well that the plan anyways thus it does not count as doing anything against trade routes). You can have city in shitland, surrounded by glaciers, and then all its "workable" squares contain enemy units, thus under total siege in a middle of nowhere, and trade routes still are not affected!
As for GT8, au contrare, would be my guess. I'm not sure how much time did north spend on caravans, but we did spend a lot, as we have seen the disadvantage your shenanigans put as into. We probably had like ~30 building mostly caravans. Suppose north had higher production (likely considering terrain, so you spend) maybe 20-25, mostly on caravans (ofc maybe you did things differently, I don't know). All this time could have been used fighting real fights. (I don't know much about GT9 situation on such tings, I have 0 trade routes there, and very little info on other players) That "makes game faster" by allowing more buying is also incredibly disgusting to me, first you spend time not pushing game forward. Then everything gets amplified as everyone gets more gold, and supposedly things progress faster. But this amplification amplifies everything, including luck factors. And I find it very questionable that it even makes things faster, as if everyone leveled up equally, it does not give much advantage to anyone, thus I do not see how it makes stuff all that faster. Mind you I of course did not doe any of the "conventional" strategies in GT9, and that is on purpose. Cause I got bored of that, so now of course I'm at a severe disadvantage. And here another fallacy rears it ugly head: you have choice you can trade and do econ or you can do war. In most cases the outcome is quite clear (I have basically no hope of progressing significantly in gt9), thus the choices are limited, you if you want good chances you have to play "by the rules". Meaning there is less variety than there could be.
So far I actually fail to see those bigger armies too. I played gt6, it had no trade routes at all. Nimrod was my ally. And he showed me what big armies look like. There was no need for trade routes to get that. Mind you, that game kinda sucked and suffered most of the same, but that was probably mostly because it was island map. Again there was insane amount of time for econ buildup and then, whoever moved out with first with his sick army won (well a bit of oversimplification, but mostly). Also, don't know where you got the idea that I want bigger armies. I want more active armies. Not armies that only city hop mostly. Or armies that stand in homeland for half the game until huge numbers are amassed and then move out clearing everything. Any RTS'es I have seen such playstyle is hallmark of noob campines. Serious games have lots of raiding and skirmishes, small attacks to damage econ and similar. And anything like that is insanely hard to do in civ games, and also gives dubious results at best.
Reducing the one time bonus helps. In GT7, airports, rails, the default ruleset and vast distances made it very easy to generate trade routes that got a +1000 gold bonus. Then with this bonus, you could buy more freights to generate more trade routes -- exponential increases soon followed. In the end, one player at the extreme of the map was building tons of cities in the desert, just as a destination for trade routes.
Yes default one time bonuses are just retarded I know that, but they can be adjusted. But having trade based on one time bonuses would at least make trade have some cost (like warfare has some cost), would also enable real piracy/interception. You only gain gold as long as you build caravans, meanwhile your build slots are clogged. You switch to war, you stop trade stuff, no nonexpiring advantage from doing rather minor thing. You would have different episodes cycles, different nations having different strategies at different times. Now it much less possible, cause if you miss main wave of trade route buildup you'll be left quite far behind, so you better don't! And thus trade-route buildup likely mostly happens at the similar rate everywhere. As for rails and airports, civ2civ3 caravans do not use rails (at least my test indicate so), for airports it should be possible to disable airlifting for specific unit, maybe (my attempts at that so far failed), but that can be implemented. As for buying, well I think I said already, I do not like that concept much at all, and it does not matter what you are buying.
Also any experienced players are very welcome to point out what they see as being wrong with my reasoning. As surely lot of you have much more game experience.