How exactly in your scenario is a non-elf player supposed to tower rush immediately, yet still have the resources for tech to get siege nearly as fast as an elf can get it.
So no, you have towers vs towers and siege. Towers that can move, at that. Tinker is good in tower vs tower situations. It can either place the factory outside range of your towers and send the goblins in to explode, or place the factory inside their base to defend the glavies if you dive.
For one, a blademaster can’t destroy a massive portion of a closed off base just from casting 1 spell and sitting there.
For two, I don’t expect to always be able to chase a hero down, just to disable them if they over commit too far into my base. It’s absurd that an ultimate gives spell immunity 100% of the time. You don’t see an MK on level 6 get spell immunity for the rest of the game. There’s a cooldown, because you know, that’s balanced.
Also, a blademaster needs to use mana to run significantly faster than any army in the game. Tinker just does it all the time for no cost.