File explorer search is very slow and we will do anything to fix it, any budget.

So we manage a network for a franchise medical practice and their billing department is centralized with 11 people that do nothing but search client names and email the bill using excel. It is incredibly frustrating that they use excel and the windows search on a mapped drive to search client names. They open it in excel after the search, and then create a new bill to mail off, but they refuse to change to an application specific system.

So we have upgraded the server to the latest i7, with a Samsung 860 pro ssd(sata, not m.2), we have a 96 port gigabit switch, we have had then organize the folders alphabetically to help with indexing, but it's still slow. I'm wondering if we can just throw enough hardware at it to fix the problem or if file explorer will always be our bottleneck? I read that there are limits and it's not what it was designed for. We are reaching the end of our rope here and hoping someone out there has advise. Thank you for any responses!!!!