Yeah, integration work never ends but having a few popular ones built in + api and docs goes a long way. I've honestly never seen anyone in mid/big companies consider Zapier, but it's been a few years since I was in that space, so could have changed. Getting into those bigger companies, you're basically going to need everything, or hope for a small team within the company to like your CRM.
Those small teams/companies basically want a simple Hubspot, not salesforce, but a lot of times, they don't really know the difference. Something that can take Apollo leads, build some "simple" email campaigns [1], some landing pages [2], track one-off emails and report on all that for cheaper than the $25k/yr or whatever hubspot charges would be a great tool. I know, not exactly a CRM, but people call it that.
I don't think it matters if you integrate other providers or build it in, but having an easy setup where users don't have to go sign up, manage and integrate with a bunch of other services could help you get the small/startup space.
[1] Lots of things to deal with if you're taking on the email sending & tracking part, automated clicks, safari privacy, etc.
[2] This is a can of worms, but being able to build simple landing pages for people to click on from an email is pretty important.