Bloons TD5 is the best Tower Defense game made for Xbox One.
Check Level Scaling under the Options menu. Supposedly in Legendary Mode you should hit the cap before the end. If it's set to Classic Mode, you wont.
That's my understanding, anyway.
2 other comments
I was on Legendary Mode. Ended up at level 28. Max under Legendary is supposed to be 30.
Well, then I guess I know what to look forward too.
Kill 1000 enemies in Expeditions. - Outriders
Use crafting to replace 10 item mods. - Outriders
Use crafting to improve the rarity of 15 items. - Outriders