If your managed service provider forces you to switch to an Active Directory and Office 365, then this should be a red flag that they are lazy and are using the most profitable solution for them - not you. An actual MSP with your interests will thoroughly evaluate or assess your needs.
"Hi, we are the biggest, we are the best - here is how you should do it." - MSFT MSP Salespeople.
Buying Microsoft is like dropping an anchor in the water while at sea. It will not break the bank, but it will cost extra fuel and have adverse effects as it bounces off wildlife. If you run software on the web, and email, why the need for anything Microsoft? If the apps are on iPhone and android, why do you need expensive Wifi integrated with Microsoft - it's adding cost to you to reduce theirs. WHY?
Taking a deep dive into your company's technical processes is essential. Selecting the proper hardware, mobile tech, and security is your index to your company. From that point, figure out how to do it cheapest, analyze risk, and create functions for operations and assessments. Do not let MSPs tell you your business.