Can a landlord refuse an assignment just because they'd rather find a new tenant themselves?

Generally, no — not where your lease includes a standard that consent cannot be unreasonably withheld. A landlord's own preference to re-lease the space to a tenant of its own choosing, rather than accept your qualified buyer, is usually considered an improper, self-interested reason rather than a legitimate concern about the proposed assignee's ability to perform the lease. Courts and the reasonableness standard implied under the Commercial Tenancies Act (where the lease doesn't say otherwise) generally focus on whether the assignee is a suitable tenant, not on whether the landlord would simply prefer someone else.

That said, if your lease includes an express recapture clause allowing the landlord to terminate and retake the space instead of consenting, the landlord may be able to achieve much the same result through a route the lease actually permits — which is a very different legal position from just refusing consent outright without cause.

If your landlord is stalling or refusing consent without a stated, legitimate reason, that's worth challenging rather than accepting. A Treadstone business lawyer can assess whether the refusal is genuinely unreasonable under your lease.