I am working now in a very large enterprise on my corporate PC running Outlook and Office. Outlook is just horrible-- slow, with terrible functionality. It takes me 15 minutes to get it going in the morning. If I want to change from mail to my calendar, that's 45 seconds. Using it remotely from home on my PC is a nightmare, although that is more an Exchange problem.
You just described a bunch of problems with implementation, none of which is inherent to Microsoft software. Sounds like you have a CTO who is either oblivious or doesn't care. I can assure you that competent IT departments serve companies with tens and even hundreds of thousands of employees without the kinds of performance problems you're describing.