I do think that teachers and assistants need to accept that it is now part of the job and I believe that most do.
The problem is staffing/funding though.
Say you have one class teacher and 30 children. If you have 29 pupils who are amazingly well behaved all of the time, have no additional needs and can get on with their work independently whilst the class teacher 'nips' off to change a nappy 5 times a day, that is one thing, though I would still argue that this is still a safety issue as whilst they are in the toilet/they are not watching, let alone teaching, the rest of the class.
But meanwhile in the real world, this isn't the case in any Y1/2 class I have ever known. Few have a class TA any more-most have lost their jobs in staffing restructures due to budget cuts. Most KS1 classes will also have 3/4 children with a diagnosis or awaiting assessment for ADHD, another 3/4 for ASD, maybe 1 with an EpiPen needing careful watching, one with eczema needing creaming regularly, 3 with asthma needing meds (and recording when this is given), maybe one with physical needs-eg hoisting/partially blind/arthritis/deaf/absence seizures/needing Movicol to be mixed up and given twice a day. That's without even starting on teaching the class and supporting any children with literacy difficulties to make sure they make expected progress and pass the phonics test!
One teacher can only do so much. Yes, inclusion is great and children should be included, but without extra funding to provide additional support, that one teacher will pretty soon break.