I think the point about how much gold towers are worth compared to how easy they are to take is really key.
We definitely entered a META where taking towers quickly and easily can and does occur. It makes sense that the value in gold for those towers should be reduced.
META is defined by the easiest path: lowest risk for highest reward. If the towers provide free gold by being too easy to take, it doesn't automatically mean the problem is that towers are too weak. It could be that towers give too much reward for the risk involved in taking them. META-wise we see the Rift Herald allows for some easy tower takes. The reward of taking a tower isn't necessarily balanced by the enemy getting a tower in return. If the reward for taking a tower is too high, it helps to create a free gold into snowball situation.
There are many ways to make towers easier to take down and not any ways to make towers harder to take down. It follows that the reward for taking a tower shouldn't be as high and/or the players should have more options available for tower defense.
For example, Dragon gives a buff for taking towers down, but there isn't any dragon for making towers harder to take down. There's a fundamental imbalance in the mechanics that favors a particular strategy. There's no option for players interested in defending towers, only options for players interested in attacking towers.
I could list all of the items, buffs, and summoner spells that favor tower taking, but I don't need to because all we have to do is look at the list of items, buffs, and summoner spells that favor defending towers... it's empty. There are no supplemental mechanisms available to players who want to defend their towers. But despite the inflation of tower-taking capabilities, towers haven't taken a serious hit to their gold value. And thus, I have to agree. RIOT needs to take a look at towers risk vs reward (monetary value) as well as tower defense options.