The secret shop is pointless nowadays.

Back in Dota 1 days, there were many different shops and some of their locations were hidden. Completing certain item builds was a serious mystery back then and there was no wiki or website where you could easily find information.

On Dota 2's release, there were only three shops left, the main shop, the secret shop, and the side shop. The vast majority of items are purchasable in the main shop and the secret shop was not only clearly marked on the map but the courier had an ability that sent it straight there. Even back in 2013, the secret shop was a minor mechanic that was part of learning Dota but it could still make a difference when it comes to sniping couriers or ganking heroes near it.

Since 7.23 however, the side shop is not only removed but each hero starts the game with their own courier so killing one courier is not even that advantageous anymore. Even if you try camping the secret shop or the enemy fountain, a player could just activate speed burst to get to the secret shop fast and activate the shield to protect it from attacks on the way back.

Honestly, the secret shop is just another archaic holdover from Dota 1 days at this point; no different from Unique Attack Modifiers or Movement/Attack Speed limits. It is not secret at all despite its name and there really isn't much the enemy team can do to deny you from access it (not like any team would bother doing this anyway when they can just farm or siege towers or take Roshan). The only other purpose the secret shop serves is that you can't quickly buy secret shop items before you die, but a skilled player can just pre-buy the secret shop items when they have the gold.

I have played over 2,000 matches of this game and there hasn't been a single time in 9 years where the secret shop mechanic contributed to me winning or losing a game. When you play game modes with a universal shop like Turbo, the fact that the secret shop is no longer needed just streamlines the game without seriously affecting it. If Valve wants to promote the game with the anime and help bring in new players, they should make the game slightly easier to learn and get rid of it. They can still keep the shops or even replace them with trees, just make everything purchaseable in the main shop.