If the executor does not comply, the court may appoint a new executor or agree to a new executor that the beneficiaries or heirs propose.
An executor or administrator could violate the terms of a will by doing something without court permission, in which case they could be held personally responsible for returning the funds that were compromised as a result of the violation.
Executors can and are excluded. Even Wills written by solicitors can be ignored; Solicitors, and Will writing agents know this, but they still continue selling this drafting service which is not fit for its purpose.
Executors can withhold monies from beneficiaries, though not arbitrarily. Beneficiaries may be unable or unwilling to receive a gift by a will. The executor's job is onerous and the time taken to execute a will may vary greatly.